1994 - 2002 GM Truck Twitchy Erratic Crazy Fuel & Oil Gauge Needle Aircore Motor Repair (Chevy GMC)

This video goes over ONE possible cause for an erratic (crazy spinning needle) fuel gauge for old body style (OBS) GM trucks and vans of the 1990s and early 00s from Chevrolet, GMC, Holden, & Cadillac not working. In many cases the vibrating, twitching, bouncing, fluttering, and related unexpected jumpy behavior from the gauge has nothing to do with electrical grounds or the fuel tank sender, it is simply the effect of age on the aircore motor of the gauge itself. The original internal dampening effect is lost, corrosion sets in and the air core motor gauge becomes unreliable and must be replaced. Note that I said "aircore motor", there are NO stepper motors in these years!
The vehicle illustrated is an OBS (old body style) 1999 Chevrolet K1500 Suburban with the 6.5L diesel engine, but the symptoms and repair procedure apply to all GM trucks and vans of the same general era - before the introduction of stepper motors beginning in model year 2003. Of course the cluster disassembly I show is 96+ OBS only.
These motors were never sold by GM. NEW ones are in an OFF WHITE plastic housing color, whereas the originals were typically a yellow color. You have to pay attention to the calibration code letter in black on one of the housing ears as shown in the video. But DO NOT BUY USED yellow original ones - the air-core motor calibration is from a fluid internally that degrades with use and age so every original has the dampening defect to some degree as well as corrosion - so you'll be risking a failed repair by buying used. You can only fix the erratic behavior reliably by installing an (NOS) NEW air core motor OR a speedo shop remanufactured one. Each GM gauge type uses a different aircore motor calibration, so again please take note of the letter codes below!
Original calibration codes:
F = Fuel gauge (94-02 OBS trucks only)
C = Fuel gauge (1999-02 NewBS trucks only)
P = Oil Pressure gauge (94-02)
V = Voltage gauge (94-02)
S = Speedometer and Tachometer (94-02)
S = Transmission Temperature gauge (1999-02 NewBS trucks only)
T = Engine Temperature gauge (94-02).
If your fuel gauge needle was way off you will have to get access to a new fuel tank sender, hook it up and use it to calibrate the empty, 1/2, and full positions accurately. You can similarly re-calibrate major differences in the other gauges by replicating the source sensor input.
The eBay and Amazon search links below are paid links, for which I may be compensated and earn a commission, if you choose to buy the parts and tools shown in this video thru them:
Those still selling the "F" new - ebay.us/VqEbdY or ebay.us/nud8nD and one selling rebuilt - ebay.us/2SHX5a
All calibrations (skip over the yellow used ones unless they are rebuilt): ebay.us/OKZvii
C calibration: amzn.to/34OvXnD and the S calibration: amzn.to/3lLGBAS
GM 25089350 / ACDelco part number PC195 (replacement instrument cluster bulb) at eBay: ebay.us/nfUgt4
Alternatively Dorman has a complete remanufactured cluster for these trucks. Dorman 599-350 for auto & Dorman 599-460 for manual trans: ebay.us/HED3wc
Here's the GM service manual: ebay.us/2vlHP3
NOTE: It is very important you first eliminate a faulty fuel sender, bad grounds between your PCM and the fuel sender & the instrument panel. Your fuel sender is sending an analog signal to the PCM. The PCM is converting that to a digital square wave signal it sends to the cluster. The aircore motor for the fuel gauge is calibrated with a dampening fluid to smooth out the high and low points of this digital square wave signal. When that fluid degrades, the twitching begins. The gauge is otherwise accurate, until the aircore motor completely fails internally and then points off the gauge.
And if I've saved you some $$ here, consider some coins for the coffee tip-jar! ko-fi.com/drshock
Chapters:
0:00 - Problem overview
1:25 - Removing the IP cluster
8:32 - IP cluster disassembly / aircore motor removal
14:37 - Replacement aircore motor installation
22:59 - IP cluster adjustments and reinstallation
#drshock
Disclaimer: DrShock, the alias for the human content creator for this KZbin channel, is not responsible for any damages, injuries, losses, or liabilities associated with any repairs, upgrades, or maintenance performed on yours, or any other, vehicle whatsoever. No warranty, express or implied, is made as to the accuracy or completeness of any information provided within this channel. Viewing and using the “as-is" information of this channel is totally at your own risk. Always wear personal protection equipment and follow appropriate vehicle manufacturer service manual guidelines with original manufacturer parts only when performing any repairs, upgrades, or maintenance upon any vehicle.

[@DrShock]

PSA: Guys the supply of these replacement Air Core Motors seems to have dried up and they are much harder to find now. Several links here and in the video description text to help you though. Try all of the links on both eBay and Amazon to find the best price for the calibration(s) you need. They were available for a time as outfits like Dorman that were remanufacturing these dash clusters, as well as local speedometer repair shops, provided enough demand to warrant producing them still. But as of March 12, 2020 they are basically in the new old stock (NOS) stage now and every one of them will be an easter egg hunt. The "F" calibration is the hardest to obtain now, I see only two sellers on eBay affiliate linked below: One seller on eBay, USDashWorks, who is selling the actual units I have bought in the past, has them back in stock. They have a core charge now though and he's got the "F", "C", "P" "S", and "T" calibrations currently - ebay.us/VqEbdY. Here's another I found - ebay.us/nud8nD. Here's a third seller, selling refurbished "F" calibration air core motors - ebay.us/2SHX5a (remember anyone selling yellow plastic housing motors are selling used pulls or rebuilds, not NOS). I'll update this pin if the supply situation should change. Remember the used yellow original ones will not fix the needle dancing problem my video covers for the "F" or "C" fuel gauge air core motors, but the used yellow ones should be fine for the other gauges in "T" "V" "S" and "P" calibrations and to correct a completely inoperative / dead gauge situation.

[@Monuments_to_Good_Intentions]

DrShock I am going through a bunch of these 6.5 videos once again because my truck is broke down once again. I hate this truck. I really hope I can earn enough money to buy a new truck soon. Good video btw. If I cared about my truck, I would do this swap.

[@CarlCowles]

I'd like to add that we have remanufactured "f" motors and they are good to go. I have the original applicator to inject oem fluid into the motor. The "f" motors are permanently out of production. The remanufactured F motors are the only option now. Visit www.usdashworks.com to place your order.

[@GeekBoy03]

I am having a different issue in my '94 Suburban. I can tell when the oil is getting low when the oil gauge starts twitching. I get low on oil quite often because I am using that special Mobile 1 0W-30 for better fuel economy. For the fuel gauge, I think it was not calibrated for the fuel tank. From the factory, it came with an optional 45 gallon tank. When the tank is full, the gauge goes way past the F line. The lower the gauge goes, the more accurate it becomes.

[@DrShock]

@@GeekBoy03 Past full line really sounds like a sender problem. This video might help - kzbin.info/www/bejne/mqiceZyXapqsr9U as the test it covers is for both gas and diesel.

[@pulpo.r7790]

If you can find new replacement, the white ones will work for fuel level? I went to the junkyard and found a F gauge. And it had good resistance so I replaced it but it still vibrates. I adjusted the gauge as follows. And I also replaced the fuel pump. Due to a fuel sensor level code. So I’m sure the fuel pump sending unit was bad and the gauge was bad as well.

[@km6344]

FINALLY!!! A video that not only is exactly the issue I have,, but also a step by step as you "show" the steps where there are no gaps where I have to guess or wonder any of the steps, like other how too videos on here! Thank you for this video! I was about to replace the expensive sending unit! I woulda benn so pissssed to find that wasn't it!!! thank you!

[@brandonstennes4931]

In the future when the next gauge in your truck goes crazy twitching. Try using super lube silicone oil, used that on my fuel gauge it was doing the same thing, twitching and going crazy. The fuel gauge works like a damn now.

[@benkanobe7500]

None of us could ever be expected to be able to do this without your outstanding video! Thank you so much!

[@condeerogers5858]

Great video. You have helped a lot of people with this problem. I am one of them. Thank you.

[@randallsutton4168]

me too!

[@macgayver496]

Enjoy the coffee! Had to replace the gauge cluster stepper motors on my 2002 Buick LeSabre. The Buick's erratic oil pressure reading was just the sensor; same thing on my GMC. LeSabre fuel readings were the sending unit on fuel pump. Thanks for the videos.

[@arabcampers9554]

I had this fuel gauge problem in my 1999 suburban and its driving me crazy I did a lot of researches and many peoples were talking about changing the fuel pump clean the ground terminals taking the gauges out and clean it with alcohol its all worthless solutions , a close friend to me knows about me having this problem he sent me this video as Christmas gift I'm serious that was my Christmas gift and guess what its the best gift I ever got in my life because this video CLEARLY showing me the problem and how to fix it straight forward , Sir you saved me from getting rid of my 1999 rare Sony edition suburban .Thanks a lot and Merry Christmas .

[@DrShock]

That's great Merry Christmas! Here's another one, as sometimes this behavior can be the fuel sender too - kzbin.info/www/bejne/mqiceZyXapqsr9U

[@MrBowNaxe]

Excellent video! I've watched it several times and feel confident I can finally fix my '99 Suburban after all. Thanks for sharing this video for all of us!

[@JoseMartinez-we1ux]

AWESOME! I have the same issue. Been trying to figure out what is wrong with my gas gauge for years. Thanks!

[@justwigs]

I HAD THE SAME PROBLEM A YEAR AGO REPLACED THE FUEL PUMP FIXED IT,ON 1998 GMC SIERRA EXTENDED PU 5.7L

[@tarbeau8561]

DrShock, I too get to do this with my truck sir. But, thanks again for sharing your knowledge and videos, it won’t be as hard as I thought it was going to be. Thanks again for sharing your videos so we all can learn something about our trucks or SUV’s.

[@paulking2279]

Thanks for the video! Definitely saved me some time! No more vibrating fuel gauge!

[@jameslewis1175]

Man u have the perfect voice for narrative informational videos. It's like it's easier to absorb knowledge fromya

[@pup734]

I really find your videos on these trucks really helpful thank you

[@camarokurt]

You saved me from pulling the tank on my Suburban. Thank you.

[@jaimerios995]

I have a 99 gas suburban. Did that fix your issue

[@makingtechsense126]

Great video! My fuel gauge is starting to develop this problem so now I know what to do to fix it.

[@stebstebanesier6205]

Thank you, not only was this video very helpful, but for the most part it wasn't shot by you holding the camera in one hand while trying to do the repair with the other hand. So kudos to your camera person, and i wont even discuss video that are shot vertically.

[@denniswoods8894]

Thanks!! My 97 Yukon fuel gauge has the shakes!! Keep up the good work with the videos 💪🏾

[@WillCtheMechDrummer]

Great video bud!!!!!! I’ve done these before and just bought an old truck for myself. Needed a refresher… thanks! Subscribed!

[@Twin_Flyer]

Excellent video, thanks for posting it and the link!!

[@PastorJack1957]

My 1996 gas fueled Tahoe has the same issue. I find it interesting a diesel would also have the same issue. Thanks for posting!

[@LetsFigureThisOut]

Just repaired my Safari using this video. Thanks

[@guillermobuenohernandez847]

I have a 1999 Chevrolet Tahoe and my fuel gauge is at full tank when I have a quarter tank ,. Thanks to this video I have the link so know I can buy this part for my cluster.

[@scout4locations]

Oh man, this was both hilarious ad informative. I just found a sealed and preserved GMC SUV cluster that hss a tach that goes to 6 whereas, my 1995 Yukon has one that goes only up to 5. So, I one found in a field out in the desert. The desert sands are used frequently by illegal trash people and the stolen vehicle mafia for parts dumping. It has sand inside it but I am still going to try it out. And here is shocking reason why: You see, I too am suffering from the painful and expensive disgrace of living with the embarrassment of having the insidious condition of The Fuel Gauge Twitch. Hiw much gas do I have left? Thats that little dials only purpose. To let me know that I could be stranded by you in 20 miles. Now I have to do the MGP math. Then remember my miles. Wow, fuel gauge, I never realized how much you really do for me. Thank you.

[@BigWheel.]

Thanks for the video! I just bought a 97 yukon GT two door, and the fuel and oil gauges fluctuate. Hopefully now I'll get it sorted.

[@adamx6186]

Holy crap, no wonder my new fuel motor didn't work, I missed the crucial step of swapping over that tiny resister from the old motor. Too bad I had already thrown it away, but luckily I had just bought a parts cluster cheap for the temperature motor. Great video! Thanks

[@MrJdub20tx]

My temp Guage is acting funky too I changed both sensors already too

[@irredeemabledeplorable5227]

Informative video...thanks...I only wish people would check their volume when producing these vids...We can ALWAYS turn it down if it's too loud...lmao

[@ronmiller682]

Thank you for sharing your knowledge, this is exactly what needs to be done to my 98 truck and dads 99 tahoe.

[@chrisschultz6541]

Did this to my '99 tahoe. Seems to be working so far. Tip: fill your tank full before. Don't try and fit every single drop in your tank. Just go the the standard first click at the pump. When you first turn it on, the fuel gauge should adjust itself to full, it is slow. Let it go for a minute or 2. Key off, adjust needle and do it again. Run it with the cover off for a little while and watch your gauge, make sure it continues to read correctly. Go to 3/4 tank, fill up. Do the math for your tank size and it should be good. After you verify, close it all up. Gauge motor delivered was about $104.

[@franksteve5594]

Whereabouts did you purchase the gauge from?do you have part number?

[@KYoss68]

Temp gauge pegged itself at 260 the other day but the engine didn't seem unduly hot. Will investigate further but I bet it's going to be this. Thanks for the comprehensive video.

[@juanreynoso9653]

Thank you I enjoy the video very much I totally appreciate what you've done.

[@johnk7050]

Perfect! Yukon getting and trying to keep together because I still like it. Was able to do with your video help. Thank you.

[@david206820071]

Just finished my part now next step will be installing everything back and see it working back to normal

[@shawnswnh1054]

Wow glad I found this video, my 1999 suburban fuel gauge is doing the same thing, I was dreading dropping the 42 gallon tank but will try this first.

[@jaycrawford6498]

I have a 1993 Chevy diesel. Is it pretty much the same procedure. Also are the parts the same.

[@billstonesmith9231]

Great job Dr Shock!

[@fulgenciomarcos9350]

Finally I found what I need. Thank you.

[@justpaynmydues]

LOVE YOUR VIDEO! DECENT INFO ON PROBLEMZ WITH THE GUAGEZ! I RESPECT THE TYME YOO TOOK TO LET OTHERZ KNOW WHAT COULD BE WRONG. KEEP UP THE GOOD WERK!! 👏🏼👏🏼😁😁👍🏼

[@KnuckleHeadGarage27]

Yep I have a 98 Chevy Cheyenne 2500 5.7 and does this . My oil pressure gauge seems to work but my oil pressure isn't good when gets hot but my temp is off and my gas gauge is off

[@josepalacios9020]

Thanks man great video

[@brettpresser2256]

Very well done video it was extremely helpful

[@apsonyo2407]

Great video hope other people learn that you need a camera person to do this kinds of video and not trying to do everything with one hand love it I think I can take on my own instrument cluster thnx

[@jorgefonseca9225]

great vedeo mate you save me a lot money great explain!! cheers from norway

[@theon_ean_donly]

Wow never expected to find this video thank you so much blessing 😊

[@greddmyles3677]

OK what about this, my fuel hand was going crazy so i changed the sending unit. I emptied all of the old gas out put ten worth in the tank start it up then the hand was like over from the E a bit, before I cut it off I noticed it was on F, and stayed there. So where do I put the needle when I fix it?

[@nonameisthename138]

WOW!! I wasn't looking for this video, but my RPM needle has just started to do this occasionally on my 92 Silverado. Thank you, and great job!! I know what to do for it now..👍

[@bucksmith9035]

ive got an astrovan does the same gauge fluctuation was told sending unit in tank now ill replace this unit first thanks for this video

[@cheezblock4lllll]

ive looked everywhere for the tool u use to take the needles off cant find it anywhere must be a rare tool lol good vid thanks for the walk through. good info

[@DrShock]

Yeah super rare to have one clean for this application, if you mean at 12:33 it is the highly useful forkomatic from Chick-Fil-A. ;-)

[@allentuggle6732]

I appreciate you looking at your video and coming back to clarify.

[@JorgeTorres-lj6dt]

Fantastic buddy thanks for your help

[@bobcormier5098]

Good job bud......now I no wuts going on with my fuel gauge it flickers here and there .....I have 1997 gmc savana van. But it says gmc truck on the van. But verrrry helpful thank you

[@poncetorres7110]

Grate video nice thank you for sharing. ☺👍🏻.

[@hermthegerm4039]

Great info thanks very much

[@1deadpool11]

Good man. Thanks for the info

[@mikehuff7294]

Thank you! Very very helpful

[@snickerstorino]

gm has a great reputation for faulty dash and electrical issues in the 90's and early 00's. just an fyi if the oil pressure sensor goes out in yours depending on if it shorts or loses connections it can peg or show zero. zero return reference from the sensor in my 92 causes it to peg out, just some food for thought. if the sensor in my 92 actually sends a zero signal it kills the fuel pump. i recently had it go bad and for a year it was pegged. replaced the sensor and away i went with finding other things that were bad too. This said one wire on my 92 goes through the fuel pump relay and back to the pcm, one of those is a fuseable link so if its damaged that can screw with readings too. Best thing to do pull the sensor and check the pressure manually, this will tell you if the gauge or wiring is the issue. If the oil pump really is bad and the sensor is working it will kill power to the fuel pump. If the cluster is screwing up it will still throw the check gauges but will never kill the engine.

[@DrShock]

Thanks, good points. FYI that GM safety design ended in 1995. The oil pressure sender from 96+ is no longer involved in the fuel lift pump circuit.

[@snickerstorino]

@@DrShock interesting, I didn't know that but thanks for the info. I just wanted to share my recent experience with my 92. I had a 99 suburban with dash and fuel pump issues but the pump had power so it was a no brainier and the cluster has shitty grounds everywhere.

[@snickerstorino]

@@DrShock you wouldn't happen to know if these are the same motors in my 92 would you? i think the motor is weak, the oil pressure is different than the gauge according to my manual gauge i hooked up. it also doesn't come up with rpm increase sometimes but does other times and other times it drops to zero after its hot and then when i restart it goes higher but slowly drops back to zero. i suspect the motor is weak because it was pegged out for a while when the sensor was shot. i haven't torn it apart but i wondered if it was, thats actually what brought me to your videp

[@DrShock]

It's going to be the same aircore type gauge design, but I do not know if it's the same part used on the later models or not. Even the ones I did this video have had their supply dry up during the pandemic though. I pinned a comment at the top of a speedo shop on eBay that offers a rebuild service. You might ask those folks.

[@snickerstorino]

@@DrShock thanks, i appreciate your time.the salvage yard has a cluster so i might try my luck there. hoping my amazon oil pressure tester is right, i don't want to do an oil pump. the gauge is acting a bit strange, my only concern is when the gauge hits 0 oil the check gauges comes on but if i manually push it over it doesn't trigger the same warning. so i don't know if the gauge triggers that or the switch itself. not sure exactly how those operate but i will put this other cluster in and see what changes then swap the motor if thats it and keep the rest for future use if the motors are all gone. the yard only wants 50 for the whole cluster but who knows whats good in them. again thanks alot for your responses

[@ezequielpena5492]

Man I’m glad I found this video!! I have the same problem on a 1999 suburban!! I’m going to order parts to get her fixed

[@jaimerios995]

Did it fix your issue

[@nafeesahmad9761]

Good information 👍🏼

[@jimmytorres111]

Great video

[@bobbiesawada9460]

I hope that I can find these motors, going to replace the factory radio while I have the bezel off , it still has the factory AM/FM Delco radio.. Any help locating these motors would be a help.

[@DrShock]

Supply from China has dried up. Pinned comment has the only source, an eBay seller, left who has some stock and original equipment to refurbish used motors as well.

[@justfixit9726]

My gas gauge spun like a clock and just like you said it took out the oil pressure gauge. 99 k1500 5.7 suburban. Its a shame it went bad altho i had to replace the stepper motors in my 04 yukon 2 years ago. So it lasted longer (suburban) then the next generation factory replacement(yukon).

[@bobbiesawada9460]

@the section about the bulbs , these are all 194's? I assume these are clear bulbs wondering if I decided to use maybe blue if it would affect the orange needles..

[@DrShock]

No, not all of these are 194s. Some are different, see 6:53

[@lambertsaldi1550]

Awesome Review thank you 👍 🇺🇲

[@redlightrunner930]

Well off to the internet to get new guages. Good video.

[@bobbiesawada9460]

I have a 1995 Chevy S10, the oil pressure gauge seems to go crazy and give odd readings and my tachometer needle stops at 1000rpm when I turn off the engine. I can tap the cover and the needle goes back to 0. Is it a air core issue?

[@DrShock]

If tapping on the cluster lens affects the needle position, then very possibly. This problem is typically a fuel gauge only problem, so I wouldn't immediately jump to this as the cause of incorrect oil pressure readings or the tach without further debug and analysis. But if the needle is affected by "tapping the glass" that certainly sounds like a problem with the motor to me, perhaps in conjunction with something else though you may still have to diagnose separately.

[@davidjones7423]

I have a 2000 obs 1ton classic My fuel gauge reads about half when it's a full tank. When the key is off it zeros out. Your video shows it doesn't go to zero/empty with the key off. I'm trying to re calibrate it too read full. I have a full tank now.

[@JasonTylerRicci]

My 2000 Silverado gas gauge isn't twitchy. One min it's on empty, the next it'll jump to full (just filled tank). I fill tank, it's still on empty, then a few mins later, it jumps to full. This goes on and on. Now it seems to be stuck on full, even after driving 95 miles. Stepper/aircore motor? Sending unit?

[@DrShock]

2000 Silverado would be stepper motors not aircores, totally different tech. When I replaced the stepper motors in a 2004 it was because one of them had gotten to where it was upside down and off the scale. I've seen other symptoms where they just get stuck. So it could be your stepper motor, probably other videos that dive into diagnosing that more specifically. Could be just bad grounding though in the sending unit harness path.

[@ralphpomm4943]

Thank god for smart people 🙏. Thank you

[@nicky9148]

Same issue..my gas gauge jumps from full to empty..I have just been making sure I keep it full at all times

[@bobbiesawada9460]

Found on Ebay through US_Dashworks , a new oil pressure Air Core stepper motor for GM 95-02 , but under vehicle fitment chart it says it won't fit my 1995 S10. Now I'm confused. Help.

[@DrShock]

I can only say these fit the full size trucks and vans, I've never opened the dash for the S10 to see if they are the same size and numbers. Those guys at US Dashworks are a speedo repair shop, they are going to know if it would fit.

[@SimonTekConley]

I just learned the truck had a cup holder.

[@marioc.bitanga1974]

Great video awesome ....information now I can order my voltmeter air core n c if it will fix my discharging problem

[@laredo1307]

I have a bouncing fuel gauge that I assume has to do with a broken slosh baffle in the tank. I haven't checked to confirm but now I'm wondering if it's the same cause as this one.

[@bobcantrell2628]

Where can you find these at I am not finding them

[@donaldlong9649]

thank you

[@thebsmithimages6544]

What if the fuel gauge works but it’s not accurate? I have this issue on my 1997 Sierra k1500. Thanks

[@DrShock]

I would check grounds and the fuel sender assembly in the tank for this issue.

[@rjmaksym7692]

Having an issue on a 97’ 6.5 K2500, Oil pressure starts above 40 and drops to near 0 when hot, motor doesn’t sound strained or at lack of lube, I changed the OPS, no change, I did not notice the gauge jumping like yours, but do you think it could be a Gauge and or Wiring issue? I’ve never bought a Chilton’s or Hayne’s Manual, would that include wiring diagrams?

[@DrShock]

I've only used the GM service manuals, so couldn't say what's in an aftermarket manual or not. This sort of symptom isn't enough to make a root cause determination. I would start with measuring the output of the oil pressure sender, or even connecting a mechanical pressure gauge. From there you'll want to verify the oil pressure signal wiring into the VCM, and then on to the IP cluster.

[@kennethstevenlilley4798]

Can anybody find or give a link to an aircore motor for "F" fuel ? For a 94 c1500? Will another year air core motor fit ?

[@terrybartruff9460]

My temp gauge usually read somewhere around 200 degrees but suddenly started reading about 180. I replaced the sender unit but it did not make any difference. Do you think the gauge is the problem?

[@DrShock]

If the gauge consistently rose from zero up to 180, no that would seem to be normal aircore motor operation. If I had this situation I would check that the thermostat is operating correctly.

[@Abdullah-Alamoudi]

Very helpful video. Great job. THANK YOU SO MUCH.

[@larrygocha9494]

I have a 2000 Chevy 3500 with a 454 engine my fuel gauge stops reading at a half tank it will read full when filled it also seems like the needle vibrates when sitting still do you think it could be the gauge.

[@DrShock]

Vibrating needle problem is what this video was about, but reading wrong is more likely the sender. The linked video in the upper right of this one might help with that. I've seen both needing replacement with these OBS trucks being over two decades old now.

[@user-yu8cx5ot7p]

So i have 94 suburban and it was transmission. Now its gearbox and i want active the sift up light... its comming without (K) wire... so i want to beldup (K) wire tell me start from.... And finish in where and thank you 😊

[@DrShock]

If I understand your ask here you have a 1994 Suburban that originally came with the automatic transmission and you've now swapped in a GM manual and you want the instrument cluster shift indicator to illuminate as it would if you had the manual trans factory installed by adding the missing wire from the harness. Well, you have more than a missing wire to deal with here. To do this you would have to be using one of the original two manual transmission types that GM originally shipped RPO with the Suburban in 1994, AND then you will also need an ECM (engine control module) from a 1994 truck that was equipped with that SAME manual transmission type AND the SAME engine type (diesel or gasoline) as in your Suburban. Lastly you'll need access to a GM Tech2 scanner to reprogram your Suburban's VIN into the swapped ECM and possibly update the calibration for the particular engine. The wire at the instrument cluster is missing due to differences in the factory ECM wiring harness between automatic and manual trans equipped trucks. The manual transmission shift indicator signal is driven by the ECM computer, but programming to drive it will not be present in the calibration file for an ECM installed with an automatic transmission. So AFAIK it's not possible to just add the wire, because the automatic type ECM in 1994 won't have the programming to drive the shift signal for the manual trans. GM had separate ECM part numbers for each powertrain combo (engine + transmission type) in the 90s.

[@davidg813]

What's the stuff a person from spinning back that mileage gauge while they're at it

[@angrybobking5083]

my 1996 suburban, gas, with stock tire size, the speedometer is off by about 5 mph, is that aircore motor the problem?

[@DrShock]

I would say unlikely, presuming speedo shows zero when you're not moving (if it does not then it could be). Given original RPOs for axle ratio, tire size matches door jamb sticker and all four at correct air pressure shown on that same sticker, and original transmission everything related to calculating the speed is handled within the powertrain control module for '96 based on various sensor inputs. The aircore motor is just going to reflect that pulse signal sent to it by the PCM. Pre-96 I believe there would have been a vehicle speed sensor buffer board that calibrated this outside the PCM, but I believe 1995 was the last year for that on gasoline (diesels would still use it) and this link is great for how to adjust it for changing tire sizes/axle ratios - tbichips.com/?page_id=504 in case someone sees this comment with an older truck. So my initial reaction to it being off such a small amount is simply it being over two decades old now any or all of the electrical sensors involved may have "drifted" in spec. But you might get lucky with google with some of these new terms and jargon I've given rather than having to resort to parts swapping to trace it down.

[@anthonymendoza4343]

Could it just be the ground wire itself from the sending unit that causes the erratic fuel gauge because I already replaced the fuel pump with sending unit itself and same goes for cluster I replaced 3 clusters and nothing fixed the erratic gas gauge?

[@DrShock]

Yeah, there's a couple of difference dances that could be going on. The _twitch_ is always going to be the aircore motor in the gauge cluster. The _wave_ or the _sway_ is going to either be the sender as well, or the wiring harness to / from the gauge. Either to / from the cluster to the PCM/VCM, or to / from the PCM/VCM to the sender in the tank.

[@aaronsmith1079]

i have a 97 that when i turn the truck on it looks all good on the cluster every gauge and light are working the blinkers work, light comes on and goes away like it should same with the hazards, the problem i have is when i turn on the headlights all gauges go to zero and my temp goes all the way past hot rpm and speed drop past zero ? help if you can .

[@DrShock]

I'd have to say reads like a short circuit but I have no experience with this particular scenario. When you turn on the headlights that also triggers the backlighting for the cluster, I would start by tracing that particular circuit using the wiring schematics in the factory service manual to see where the damage might be that you have going on there.

[@user-vs8ox4hj2q]

I have the same issue with the fuel gauge but I replaced the fuel pump and I replaced a cluster and still doing it any help please

[@DrShock]

This particular problem I cover in the video has nothing to do with the fuel sender in the tank, and unless your replacement cluster was rebuilt with new aircore motors it too would likely suffer the same gauge problem after so many decades. The only real fix is the replace these aircore motors themselves, presuming this is the problem you have where the guage needle moves even when the vehicle is parked and still. One thing you could check though before going to the video work is to inspect all the key electrical grounds on the vehicle. A bad ground (wiring, fasteners, and connectors) can also affect the fuel gauge behavior at vehicle rest.

[@bert2423]

So I have a 99 Tahoe same engine. It's been sitting for 10 years. I just did the restore with new parts [water pump, thermostat, hoses, etc.] The temperature gauge reads over the max point and it shows warning check gauge light. Could this be the same issue?

[@DrShock]

No, this vid is primarily about the fuel gauge which has a particular aging flaw in the aircore motor due to a dampening fluid that dries up inside. The other gauge aircore motors can go bad too, but they tend to fail outright (non functional) or read wildly off scale (like the damaged oil pressure gauge aircore motor in this vid). The check gauges lamp is on because your temperature gauge is reading into a danger zone. The lamp fires off to get your attention on that. For this situation I'd suspect more one of the following (air in the cooling system from not being bled fully, substandard thermostat if not a genuine GM part, defective temperature sender, gauge failure, or a problem with the wiring harness from the sender to the engine computer/cluster). Access to a service manual could speed up figuring out which, but if it always reads max I would start with the sender, and then the harness. If the gauge never moves, then I'd try swapping in an used aircore motor before buying a new one.

[@elijahrodriguez444]

Dr.Shock, my gauge recently started doing this and I was looking for the silicone oil and the one you have isn't available anywhere around me.....any substitutes that I can use

[@DrShock]

I didn't mention anything about using silicone oil, in fact I recommend against that. It's a temporary hack, not a repair. The links for these aircore motors are in the description, they are available just not cheap. ;-)

[@jamesharrison6201]

My 98 with the 4.3 is doing the same thing. Though when driving, the oil pressure settles down to 60.

[@philipdangerfield743]

I have a question, I did do something stupid I didn't mark exactly where to put my indicators back is there anyway to get them back in correct location. I did try to relocate them with key on engine off but I am not doing so well. Any help would be very helpful.

[@DrShock]

Depends on the gauge. For the voltage gauge you can measure it with a voltmeter to calibrate it. For the oil pressure gauge I mention in the video that one always starts at zero, as does the speedo and tach. For the fuel gauge you really needed to mark it as I showed, or at least have a photo as it cannot be easily calibrated otherwise. I have not tried it myself, but technically you should be able to calibrate it using another known working spare fuel sender outside of the tank (you'll have to get access to the fuel sender harness on top of the fuel tank to plug in the spare here). A less accurate but possibly still useful approach could be draining the fuel tank and setting the needle for E, then filling the tank FULL as you would usually till when the gas pump nozzle shuts itself off and setting the needle for where around F you recall it being in that state before you leave the gas station parking lot. Both approaches of course with the key in the on position but engine off.

[@philipdangerfield743]

@@DrShock Yes I have thought about that. I do have one question about part numbers. My oil pressure gauge starts with P and I have found online a new one (air core motor) how ever the numbers don't match. Example mind maybe P9876 and the one online is P8765. My question is as long as it's start with P do the numbers matter. I assume the P is for (pressure). I did purchase a used cluster and I'm thinking that if I can rebuild it, replace the aircore motors that I can find available. It would save me from buying a new one for $400$ to $800$ Dakota digital. Thanks again My truck is a 94 Silverado

[@DrShock]

The numbers are not important, likely a date code or such. It's the letter code that is important to match for the right gauge. P is for pressure yes.

[@jonatanreisin3647]

Excelent video and explanation. Could you give me some advice to check why the PRNDL lights indicador doesn´t work. Thanks

[@DrShock]

On these years PRNDL part of the instrument cluster is fed range input by the park/neutral position transmission switch. I've not encountered this sort of issue before on the 90s trucks, but I would hazard a guess it could be a problem within that specific switch, or a problem getting voltage to the PRNDL circuitry of the cluster. You would have to get the service manual schematic and check each of the 4 switch outputs are making it to the IP cluster connector, then check that the lines for PRNDL voltage/dimming are making it. If those are good, it's a problem on the IP cluster circuit board itself.

[@jacobmahy5704]

It probably your neutral safety switch located on the trans mission

[@angelarojas3653]

Just got a 98 Chevy Tahoe, the fuel gauge is stuck past full so I have no clue where I am on fuel, I just have to fill up. If I followed this video and tried to fix it myself, do you think it would fix my Tahoe's problem and I'd see what my fuel level is again?

[@DrShock]

Sounds like your'e saying the fuel gauge needle is not moving at all, stuck over past full. If thats correct it's not this specific problem but still could be the aircore motor. But for a completely unresponsive gauge I would try other things first (check wiring to the fuel pump/sensor assembly on top of the tank, check grounds at the engine firewall and frame points, and then I'd pull the instrument cluster and see if the guage is mechanically stuck or I can move it with my finger). Fixed and stuck could be several others things to eliminate first.

[@SMR_-sb4ck]

Can someone tell me why the oil pressure in start of video was pegged to the max passed 80 at idle, then at the end once job completed, truck was running at idle and guage showed 3/4 on the needle or 60 at idle? At both those times the engine temp was the same, right at start-up.

[@DrShock]

First this is a diesel engine with a different pressure signature than gasoline. Second the max peg was because the aircore motor for the pressure gauge was damaged, hence why it was replaced along with the fuel one. Idle at initial start (warm season cold engine) having 50-60psi is a _normal_ readout.

[@gn5673]

do you have experience with gauge clusters from a 1992 chevy truck?

[@Beirdo1]

I just noticed that immediately after starting my 6.5L, the fuel gauge and battery gauge decide to sweep back and forth a few times, then everything settles down. The "Wait to Start" also flashes at that time, even though the glow plugs are at temp (and it starts effortlessly, even cold). Any ideas if this is a related issue?

[@DrShock]

Doesn't sound aircore motor related to me. I'd be more looking at an electrical problem, ground issue maybe. If it were just the fuel gauge, I'd suspect the fuel sender. But since the voltmeter is also doing it I'd start checking for an intermittent ground problem.

[@Beirdo1]

@@DrShock Lovely. OK, thanks. It's odd that in only does it for such a short time, that's what confuses me. Yeah, it does sound like possible ground bounce.

[@German_MDS]

Nice video. I'm looking at ebay and there are no more "F" aircore motors available. They are selling the "C" for the fuel. Any idea if those will work? Thanks.

[@DrShock]

The most sensitive is the fuel gauge, because it's the one that actually has a dampening calibration needed to avoid the whole problem this video is about (which is caused by how the PCM sends its fuel sender signal). I would only use an "F" as originally spec'd by GM for the earlier model years. The "C" is for a later cluster. I have another truck that I need to do this same repair on for someone, and I wrote to one seller, digital-dash-solutions, who should have more "F" aircores in stock in a few weeks. I'm going to wait for the right part myself.

[@German_MDS]

@@DrShock Thanks for the reply. I asked the same seller cause he is offering the "C1" for fuel. I'll be waiting too. Thanks.

[@Bingo551]

Wow! that's exactly what's wrong with my fuel gauge. Thank you save me possible 500 to a grand.

[@Mr2004MCSS]

Nice video. I have two 98 chevrolet trucks. The half ton's gas gauge does not work and it usually reads completely full no matter how much gas is in it but will periodically drop down to empty and then go back to full. The needle also has a slight vibration to it so that it looks blurry when you look at it. I don't know if this is a sender issue, wiring issue or the gauge. The 1 ton's oil pressure gauge bounces around and always reads 80 psi initially. The volt gauge usually always reads low and my speedometer is off by about 5 mph. I would like to fix all of these issues but those motors are expensive so I may just have to live with bad gauges.

[@DrShock]

Thanks, the fuel gauge needle twitching/vibration is definitely the aircore motor itself and the subject of this video. But the gauge not working reliably, or at all, is more likely the sender in the tank. This other video I did was mainly for the diesel engine but the schematics and test process in the front are the same for gasoline. You might try this - kzbin.info/www/bejne/mqiceZyXapqsr9U Since you have troubles with the fuel, oil pressure, speedometer and voltage gauges it's more likely a cluster issue than all of those individual aircore motors going out at once. If this were my situation, I would try an LKQ salvage yard and pull an used replacement cluster myself, keeping the gauges but transferring over the odometer from my original and seeing if I get better results.

[@Mr2004MCSS]

@@DrShock Thanks for the reply and information. I will have to see if any of the salvage yards still have any clusters. The one ton truck with all of the cluster issues only has 119,000 miles on it .

[@jimmcdonald5448]

I have a 97 Olds Cutlass Supreme SL. I removed the cluster to clean and repair the lights. I also painted the plastic frame where the lights are with a gloss white. Back together and reinstalled the cluster. Everything works great.... except the speedometer. When I turned the key on, the speedometer went to 10 mph. So I pulled the needle and set it back to zero against the stop pin. My problem is that it now reads anywhere between 8 to 10 mph too high when driving. Verified using my scanner to show VSS indicated speed, and a GPS mph app. Both read the same speed. Am I overlooking something? As usual, stuff was working fine except the lights before I did this. After 40 plus years of jet aircraft engine and sheet metal overhaul/repair and repairing cars since I was tall enough to see over the fenders stuff like this happens and it's annoying. The speedometer doesn't normally move when you turn the key on and after moving the needle from 10 to zero it hasn't moved when the key is turned on. It just reads too high when driving. I'm at a real loss here.

[@DrShock]

These components can be very fragile, age an all. I would be hazarding a guess. But _cleaning_ implies a chemical that may not be vintage electronics friendly. Either the aircore motor for the speedometer was damaged by the cleaning, or damaged when disturbed from it's original mount. Fortunately, these don't have the issue with internal dampening fluid that the fuel gauge aircores do, so a salvage yard donor should fix you up there if this is the case. I'd carefully inspect the flexible circuit board for no damage to the speedometer mounting area as well though.

[@jimmcdonald5448]

@@DrShock Hey, thanks for the response. Actually it has a genuine circuit board. Phenolic material I think, but not a flexible one. I didn't touch the motors or board as far as cleaning went. However your points are well taken. Nothing to lose so I am going to try and reposition the needle at 25 or 30 mph indicated to what the scanner says actual is. (Front wheels off the ground). I'm like a kid in a candy store when I go the "pull-a-part" yards here. I have a spare cluster as well so if all else fails I will cann a motor from it. I will let you know how it goes.

[@jimmcdonald5448]

Update: The adventure worked. Pulling the needle out and repositioning it to actual speed while the speedometer is running. Took two minutes and six tries. Lowered car back on the ground and road tested. Speedometer read correctly at all speeds comparing to scanner VSS speed and GPS MPH app. I suppose this is one way to do it. Could be pure luck also. Anyway, Thank you for the video and the help.

[@Dean-Sala]

My tachometer twitchee especially when there is a small load on the system(i.e turn signal, cabin fan). Do you think this is the same problem?

[@DrShock]

No, this typically only related to a fuel gauge issue as that one aircore motor is fluid dampened. What you redescribe is more of an electrical problem. Either the alternator, or the harness paths/data used for driving the tachometer, grounds, etc.

[@jeepman3047]

What if you put two fuel pumps and even changed the stepper motor and it still fluctuates when turn or acceleration?🤔

[@DrShock]

If its an OBS truck that this video covers, there are no stepper motors. Just aircore motors. So presuming you meant aircore, then if I had changed the fuel pump/sender assembly and put in a BRAND NEW aircore motor I would suspect the wiring harness between them. You cannot use an used aircore motor, after this many decades they are all either dead or code blue by now so not a salvage part candidate.

[@sierraridgereaper]

I pulled mine out to replace and found that it has a small 3 wire pigtail coming right out of the top of the cluster, it runs over to the left vent and plugs into another small 3 wire plug. Do you know what that could be for? I searched everything and everywhere and cant find any info about it.

[@DrShock]

I've not seen anything like that factory equipped. What year?