BMW E38 E39 AUX Electric Fan Not Working Diagnostics

[@Young_23]

So did you ever fix the issue and what was it?

[@anuradhaperera549]

I identified the small box as the AUC sensor. Not a relay box. Correct me if I am wrong.

[@dolobyte]

I love it. I did not know about those two fuses in the glovebox. Great video thank you

[@lukaszstoklosa9561]

This "relay box" is a AUC sensor and have nothing to do with aux fan

[@gtarules1]

Keep these coming Nate, there are tons of people who own E39s and E38s! Most of the time, they can be the same thing!

[@robertancrum6444]

What is the part number for the relay box?

[@david-ry8wc]

I own a 2002 bmw 525i A wagon sport premium package fully loaded. In near mint condition minor scratch’s 150,000 miles running strong 💪🏽

[@TheMiniMachineShop]

I have 2001 740i and don't see 12V at the fan connector with A/C on.. suggestions?

[@quickliqproductions]

Nathan is a true BMW “fan”boy

[@stevechallis4251]

Hey Nice videos Nathan, The relay box you refer to that is located on the fan shroud is in fact an air contamination sensor inside it has a gas sensor, this senses Parts per million(PPM) contaminants in the air flow. This then controls air flow in the cabin (if air is contaminated for example when passing through smoke from a yard fire) the air flow in the cabin is turned to internal recirculation. The sensor does have a small foam filter inside prior to the gas sensor, pop the cover open and the filter can be cleaned in IPA and replaced. Works like a dream after. Hope this helps you.....

[@gilbertobernal8738]

So that means the fan just stop working if there's a fire nearby

[@alinborca3485]

@@gilbertobernal8738 no, it means that if detect smoke outside will put your interior ventilation in recirculated mode, have nothing to do with auxiliary fan.

[@SmangaPetros]

Where is ur workshop situated Nathan

[@arifs343]

Diagnostic steps noted and tried, and cost to replace electric fan is BMW genuine $520 part plus some $300 labor (E38). How good are other vendors' fans?

[@FranciscoGarcia-ql4og]

Fcp Euro might have other options maybe a bit cheaper and for sure oem quality + life warranty

[@tourima]

Could you spin your aux fan manually? Or was it seized?

[@redjstc9123]

Hey nice video man. I deleted my ac and installed an electric fan...the fan seems to never run. Is hooked up to the thermo switch

[@fredmarin9106]

Hello, I have a 1994 BMW E34= Can the A/C condenser be changed out , without removing the front bumper and front grill?

[@InternationalNova]

hello i have a question i am having the same prob on my x5 e53.. we tried jumping the fan but it would only spin for a few brief moments the same happened with a replacement fan i got from the junk yard. my question is when being jumped are the fans supposed to run full speed or will they only spin for a few moments? trying to diagnose wether my fans are both bad

[@povdrivekls8369]

hi , my aux fan is not starting when i put ac on , i have tested the fan directly is starting and is working fine , i checked the fuuses and they are ok too , ,y car is 740i e38

[@mhellcess4532]

Just want to ask where ca i buy a new fan for 2000 bmw 323ci manual transmission.thanks

[@SanFranciscoRiderr]

great video thx - question - does the AC fan turn on when you press the ac button ? thanks

[@KP0117]

Hey Nathan, can you diagnose the same problem with a X5 4.4 2003

[@andrewhippe9521]

cool you speak of that x5. I just picked one up my self but of course it has problems. big problems. head gaskets are blown water is mixing with oil. so I'm going to try to find a motor cheaply hopping I do. so if you know of any good motors laying around and have time let me know.

[@josedasilva8924]

Mate, the relay box is located on the fan itself. That little box you said was the relay box is just a pollution sensor and will disable outside air in the cabin if it senses pollution.

[@scottlogan6230]

So this is the second video I've watched by you that had the same title. I have a e 39 replaced the fan worked great for 1 month then nothing now that it's hot. Does the ambient air sensor have anything to do with the aux fan

[@ferraripure9970]

my lower radiator hose got sliced by the pully it moust of laid on ,I cut it and and put it back on shorter ,Now car overheated at idle , Could I have cut the sensor off ?

[@scottyrock6184]

Great video. I have a 2001 E38 BMW Aux fan problem. I replace my 50A fuse it was shot, I replace the aux fan. When I hit the AC, the fan did not come on. Anything I should check that I did not, Thanks

[@hueken.clarke880]

I have a 1995 740i Define in the front after radiator electrical doesn't work what could stop it from work

[@kg1574]

This has not been covered in this video AND THIS IS VERY IMPORTANT.! For BMW X5 there is a huge twist. If the aux fan does not turn on when the AC is on check the AC compressor clutch if it is not also turning when the AC is on you are low or totally empty on Refrigerant yes that's right. Check the pressure of Refrigerant and if it is empty or not have it checked for leaks and refill it. There you go your car is fixed

[@Dat550go]

💯

[@justarandomguy3969]

its not an X5 video XD

[@tr0ndizzl3]

Hey Nathan, hope you see this comment on this old video, but my E39 540i has been having an odd issue and I'm suspecting something is wrong with my aux fan. After the engine warms up, my aux fan starts blowing HARD. Like abnormally loud hard. When fan is blowing and sounding like a jet engine, my battery light starts flickering. I'm trying to rule the alternator out at this point because it seems to be charging normally until the aux fan kicks on overdrive. My question: do you think a bad relay could be causing the fan to blow harder than it should and possibly be drawing more power than it should? Or do you think it's the fan itself? Coolant temps are fine so I don't think it's a temp sensor issue causing the fan to go into overdrive

[@roberttama]

hello, my electric fan does not start when I press the air conditioner. the 20 fuse burns in 2 seconds. what could be the problem. my car is e38 from 1994. Thank you

[@universalsoldier5069]

Hi Natan, please help me with the code P0414 my Bmw e39 2003 doesn't work good

[@1stBloodyPigs]

Hey Nathan can u tell me where's the power window relay locates? On the 528i 1996 BMW. Thanks

[@leonardplanckiii998]

I think I overcharged my ac today and now it’s not working do you know what I should do to fix it ? Fan comes on but is blowing harder and louder than usual.

[@brennang02]

Just had an issue with my new/old e53. the aux fan would not come on. I actually just gave it a spin and it was slightly seized. After a couple of pushes it started spinning on its own and cleared whatever debris/rust that was restricting it and now it works perfectly. Incase anyone sees this in 2022 and your car may have been sitting for a while, give the fan a couple of turns and maybe hit it with some wd40. you may get lucky like i did.

[@Kam1kaz3dreamer]

I jumped my fan and it makes a buzzing noise but doesnt spin, and the blades turn freely by hand

[@thrty8street]

Will this process work on an m5 as well?

[@theblackmambaplague]

King Midas yes

[@Timedspark]

Oh ya more x5's and the v8 my favourite. Can't wait to see it!

[@lenniewilliams9944]

This was good

[@imdam-ned]

My 98 528i, is having auxiliary issues. It turns on when the negative and positive wires from the radiator switch, I cut them to see if it would turn on. The auxiliary fan turns on randomly. I bought and changed the fan switch, I tried 4 different relays located on the driver side that's on the fan shroad. I checked the fuses under the glove box. Again, my fan turns on, how i decided to test it was I took the Male wire that plugs in the fan switch, put the positive and negative wires to touch and turned on. Can you please help me, it doesn't turn on when I have the frost ac on. I'm super annoyed, I dont want to be buying any more unnecessary shit only to figure out my issue was simply and a $10 fix and be 2 min of labor. Lol

[@benjaminbradley9848]

Do you have a mechanical to electric fan conversion video? I can’t seem to find one and I’m sure you must have covered this topic. Love your channel man thanks for your work

[@Kam1kaz3dreamer]

I think it might be engine dependent, as my 530i has both mech and electric, just found out my elec is bad, as my mech gets loud as the car warms up

[@justarandomguy3969]

they already have a mechanical, but it needs the electrical for the ac (and apparantly overheating) but i have been driving mine for 4 years without the electric ones and it has not overheated

[@bazosmarek7981]

Could you please help me? I have following problem. Fan is working but sound is like the fan rubs against something plastic. 1. video is on cold engine (very noisy) ​@sRSA 2. video is on warm engine (I could live with that) but if is easy fix, I would like to fix it. ​@CebU Thank you very much :)

[@larryjohnson8168]

Why is the sensor connector such a bitch to get on to the aux fan switch, can’t be normal?

[@aleycat100]

if its low on freon the pressure switch wont turn it on either

[@gtarules1]

PS - when I plug in the aux fan it just runs and runs...even when the car is off. Help???

[@pheonixsheppard9657]

Hopefully you found out in the last 2 years.

[@Dat550go]

@@pheonixsheppard9657 nah he didn't.. It's still running lol

[@sergiochavez1673]

Hi Nathan, Love the content! I had a question, I have a 2002 BMW 325ci with manual transmission so I have the electric fan and it recently stopped working. Unfortunately I left the car on for a little while and it completely overheated and blew my expansion tank along with my radiator. I figured it was a bad fan and I was partly right because it doesn't turn on. I've replaced the temp sensor at the bottom of lower radiator hose with a used one in the past and now with a brand new OEM one. I've taken direct 12v power to the fan and it turns on, I've checked the fan fuse. but I still cant get it to turn on automatically with the car, I feel like the only think left to replace is the relay that mounts on the fan, however I don't like to guess. do you have any ideas?? thank you

[@vincetaliaferro2777]

Did you change the fan?

[@sergiochavez1673]

@@vincetaliaferro2777 yes it was the fan after all. I got one from the junk yard

[@theblackmambaplague]

If the fan doesn’t kick on immediately after driving the car for a while, and it takes 15 seconds to start spinning after the car has been driven, what could it be?

[@matthewrsmith10]

I am having an issue with the fan not coming on at startup with the a/c turned on. The a/c compressor will not kick on until the car reaches it's optimal operating temperature (when the water temp gauge on the interior dash reaches the middle). From that point, my electric fan comes on which I assume triggers my compressor to come up and I have ice cold a/c from then on. Any idea of what is going on in my case? My fan works in the overheat modes but not a/c mode. Help!

[@pjreynoso15]

Did you fix that issue? I’m having that same issue

[@matthewrsmith10]

@@pjreynoso15 Needed a new fan.

[@81indside]

Thank you for the tips.

[@techrepairs763]

I’m a 30 yr mechanic and owner of a Z3, bmw’s are money pits!!! U can replace something today and tomorrow something else needs repaired or replaced.

[@midgemaniaflyfishing]

Hey man I just got back in a bmw your videos are great I’ve done a lot of work using them so far on my 99 e39 538i BUT I cannot for the life of me find a few of my issues anywhere on the internet like I normally can if you see this and still check comments could you msg me ? it is in regards to the cooling system and it’s very frustrating that I can’t find the answers being that the cooling system is Very well documented for these engines/cars lol

[@NathansBMWWorkshop]

I answer a few comments still But there is way to many to answer many of them anymore

[@chrisnewbold9876]

You cant jumper this 3 wire fan, doesn’t work as its pulse width modulated. The AUC module samples the air, its not a relay, and has nothing to do with the fan operation. Video just expired with no solution?

[@midgemaniaflyfishing]

Well..did this in a parking lot and now after I removed and put the fuses back in..my car won’t start

[@midgemaniaflyfishing]

Yes I am a idiot..and yes I am currently stranded

[@chuck1607]

I really enjoy your videos & I need your help w/my overheating sensor circuit. my Veh: 1998 BMW 528I E39 built 4/98. 147k miles Background: I bought this car via an auction that came with a cracked expansion tank & leaking radiator. New parts: Radiator, expansion tank, cap, 88'C thermostat, new BMW plastic thermostat housing, new water pump with metal impeller, new double switch coolant temperature sensor, new aux fan with resistor pack attached, new connector for double switch coolant sensor...and hoses +belts.Testing:::: all related fuses in glove box tested with meter....all good (even the hard to reach 50 amp fuse). All 3 related relays were checked (1 under dash and 2 under hood), i cleaned relay pins and verified to be working correctly. I tested aux fan slow speed w/AC on, & fan works correctly. ♥ I tested medium speed & high speed using the paperclip method @ coolant connector. I inserted paperclip (brown - black w/red stripe) and medium speed worked perfectly.♥ I then inserted paperclip (brown - black/grey) and the high speed worked perfectly. ♥ I activated test #7.0 and watched water temps work as per normal (between 104c-108C). The car runs and drive very smoothly. ♥Problem: when Idling in parking lot the display temps climb above 115C and the temp gauge starts leaning towards red zone. I verified the aux fan (medium speed) still DOES NOT turn on as expected. When I insert the paperclip, the fan comes on (medium or high functions perfectly....depending on which speed I desire) and then coolant temperature returns to normal. WHAT AM I MISSING HERE?? I have the old 3 pin connector so I plan to connect it tonight to see if new coolant sensor (located lower side of radiator on pass side) is working correctly.. Any suggestions sir?

[@NathansBMWWorkshop]

Could be air in the system, , check the big fuse behind the glove box , make sure the little black relay box on the fan shroud is good, at last unhook the battery and touch the cables together to re-initiate the fan

[@chuck1607]

Thank you for getting back to me Nathan. I have good news as I believe I found the problem!! I tested the old sensor and verified it was bad. Ohms was checked at cold and boiling water on the stove and it never closed. Then I tested the new sensor installed on the car. Again Ohms was checked with engine cold & then when up to temperature. When i displayed test #7.0 on my cluster I waited until it displayed 117C. The Ohms reading was essentially the same as cold. CONCLUSION******** THE NEW SENSOR IS BAD!!!

[@cscustoms7625]

Ummm ok then

[@Blackhouseohio]

Where is your Diagnostic tool? 🤔 seems like a lot of work hunting down something that could have been found in minutes.

[@isaacaragon4725]

If anyone could help me figure out what’s going on with my E39 would be amazing So it’s been overheating I replaced the thermostat sensor, waterpump, thermostat housing, relay box for fan, replaced auxiliary fan, an fuses an it’s still overheating not sure why

[@funwithleniolianddomi3065]

Try bleeding the system if you have not

[@isaacaragon4725]

Ive bleed the system an also now at this point have replaced everything ahah an it still overheats

[@esejoker919]

@@isaacaragon4725 did you figure it out?

[@egenerationegeneration]

Try checking clutch fan an cool temp switch

[@hueken.clarke880]

1995 740i there is a light comes on dashboard trans failsafe program what causes that

[@dsmdallas2466]

FAIL ROGER RABIT: FAN NEEDS 160KZ to trigger fan to ON, + and - leads and then the third wire signal generated to ON. You cannot JUMP TEST the fan like a domestic. POOR customer buying fans he dont need then buying more and told they are bad. LOL We live we learn.

[@NathansBMWWorkshop]

Well actually the customer didn't buy anything he didn't need, the new fan was also tested on a 03 525 and it still did not work, ended up using the old fan removing the fan relay box and put it on a switch then it worked the problem was more than likely the ecu not giving signal, never had one I couldn't fix but we had to find a solution before I had 100 hours in this car, pretty much rebuilt the whole car for $300 labor, I'm sure the dealer would of got him for every penny of $7k or more

[@dsmdallas2466]

OH WOW! high five on not giving up. Thanks for sharing. I love my BMW'S but rely only on my old dodge van.

[@gjj665j66]

So it is not possible to test it? How do I know what's wrong?

[@lidiyantolidiyanto3001]

👍👍

[@elijahsd3897]

feez's. HUGE feez's