Mercury Grand Marquis - Switches To Defrost When Going Up Hill

Come along with Eric O. as he does a quick diagnosis and repair of this Mercury Grand Marquis that has a problem with the automatic heat. It seems when the customer goes up hill the heater switches to "defrost" mode. Although a modern car it still uses vacuum to switch modes on the HVAC. Let's see how to determine what is wrong. -Enjoy!
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[@BrandonF601]

See this quite often. New or reman unit is for sure the only way to go on a CUSTOMERS car. Yall think Eric O doesn't know you can definitely remove the solenoid pack and replace the o rings but its not a good move for a shop and Eric O knows this. I've done a few including 2 of my own. 98% of the time o rings get her done. But that 2% where a floor light now flickers 3 times a month and the customer just cant live with it anymore, will make you slam a module in it lol. Get it done the first time.

[@SouthMainAuto]

Yeah that is the thing. If it is my car sure, def just replace the o-rings. I install an aftermarket unit in customers car and now I have a lifetime warranty and no worries. Displays quits, orings fail, it is all covered now. A lot of DIY'ers can save a ton and just tear into it and pull the solenoid packs apart and replace the orings.

[@SmittySmithsonite]

Yeah I would never take a chance inside there on a customer's car. Especially on a unit built in '07 - 10 other things could fail in there after the repair! Better to replace the whole unit.

[@spelunkerd]

+ Brandon F Comment threads like this are why I always scroll through. From the DIY angle I'm willing to endure the humiliation of my wife's smirking complaint that I need to fix it again. I'll even eat the labor cost on the second visit, ha ha.

[@2sheetstothewind484]

You do them a favor and they`ll bite ya in the ass if they get a chance. I`m sure you`ve learned that one.

[@TheCarterHour]

Reman's are ok, but they are going to be the same as what I did in my video which the comment linking to my video. Going new is just going to give you the same problems going down the road in 3 years, because this is by design and can cost up to 1000 dollars for the unit at the dealership. My fix is going on 4 years old with no problems and 3.00 dollars of parts. I get why Eric did what he did with the Reman, hes got a business to run and has to get the vehicles in and out, but for the DIY'er you can save some serious scratch.

[@franksoliday5510]

Nice job isolating the fault to the EATC (Electronic Automatic Temperature Control) module. As others have noted, there are several KZbin videos on replacing the leaky control solenoid rubber O-Rings with silicone O-Rings for about a $buck for a package of ten ( you only need four) and about 20 minutes of your time. The EATC control head is easy to work on, no special tools required. The plastic trim piece across the dash simply peals away from the right end, no screws to remove (easy peasy). The good thing about this design is that the no vacuum default position is defrost. You'll be glad about that if it's winter time. You can also run an EATC self-test by depressing the OFF and FLOOR buttons simultaneously and then press the AUTOMATIC button within 2 seconds. The display will show a pulse tracer rotating in the center. The test takes about 30 seconds and will display DTCs if present. Depress the Blue (cooler) button to exit the test mode and retain any intermittent DTCs or depress the DEFROST button to exit the test mode and clear all DTCs. Ford recommends that you exit the test before powering off. Hope this helps with choosing to fix or replace an overpriced control head.

[@stephenlawrence4362]

Glad to see a new video. Happy thanksgiving Mr O

[@klwthe3rd]

I had this same exact problem with my 1980's Cadillac. Indeed it turned out to be a faulty head unit. I lived with the problem for acouple months as mine would only default back to defrost sometimes. Eventually took it to the dealer to diagnosis because I didnt have Eric O back then. Lol. They diagnosed it as a leaking head control unit, I paid my 89 dollar diagnostic fee and took the car home to replace the unit myself. Thats my problem, I can usually do the repair to save money but my diagnostic skills are weak. Thats why I love this channel.

[@testosteroneinc.3800]

Kenneth White Yeah! The O'ster has saved me about $3k in the last 2 years... Only problem is I want all the tools he works with, causing undo suffering to my credit cards. When he did the Snapon vid, I thought I was gonna faint. 😂 Low balance... R.I.P 🙄

[@randomron67]

If the majority of mechanics/technicians were half as thorough as you I wouldn't be afraid to take my vehicles to a shop. Wish I could call myself a SMA customer!

[@klwthe3rd]

Channel 67x We all wish Eric O was our mechanic. Get in line! Lol

[@randomron67]

Maybe I'll suggest some SMA viewing to the local shops.

[@jeffryblackmon4846]

I always learn something from Eric with each video. Thank you.

[@robinsonsmotorcycleandauto3929]

Great Job Eric always enjoy watching your channel and made the good call by replacing the unit and not rebuilding it. Exactly right about the warranty

[@CHIBA280CRV]

Everything you teach , know matter if it's a short video , that's another lesson learned for us. Fantastic Thanks.

[@damnoldguy]

Been watching your vids for about a month now, have subbed because I appreciate your integrity and professionalism

[@ronaldcach2779]

EXCELLENT ERIC O- What a great way to troubleshoot vacuum leaks. THANKS FRIEND

[@robmitchell2018]

Thanks for taking the time to post this. Very helpful!

[@john7017]

Excellent video. I'm having the same problem. Now I can troubleshoot quick and accurate. Thanks

[@lloydspooner]

I have an 03 Jeep Grand Cherokee that has the same symptoms. Now I have an idea of what to look for! Thanks for the video!

[@mikechiodetti6737]

Changed a few of these. Great Video! Installed a few of the round plastic vacuum containers on vehicles that had none. That kept the system working. The check valve and LONG vacuum hose are no substitute for the vacuum canister.

[@supercoupe6288]

got the same problem on a 03 Ford Taurus, glad you put this video out.

[@sebry25ify]

nice tip about the test port. The o-rings are what go bad. I rebuild 2 of them and the work like a charm.

[@bronzechicken4437]

I'm glad I learned what kinda core charge is on these, I have two or three sitting I bought out cars in the EOL line at the JY.

[@brianwolf692009]

Quick and easy diagnosis. Ya gotta love it.

[@richard1835]

I don't usually add a Hot-To Diagnostic and Repair into my Bookmarks Auto A/C Diagnostics Folder unless it is an excellent video with a knowledgeable source teaching it. Excellent Job on the Vacuum Actuator and Module Lesson.

[@scottramey5373]

Awesome job! Very helpful

[@macgyver2417]

Good demonstration. Thanks

[@lenb7575]

I am a new subscriber and I love your show! Keep up the great work!

[@JPilot2]

G'day, Eric, and Vanessa O!! I hope your family had a wonderful Thanksgiving! Marvelous Job on the quick diagnosis, and repair for the Vacuum Actuator! Blend door actuators can be changed by a moderately skilled DIYer with a basic knowledge of testing a simple series circuit. However, the level of difficulty can range from easy to even difficult. As you already noted, a vacuum is held in the system to make the doors move to the positions you order them to do. when the vacuum leaks down the system will go to defrost mode regardless of the position you left it in till the vacuum is built up again and overrides the spring that closed the door. the other door is the temp control door. this swaps passages from the core for the A/C to the heater core passage. It generally allows a faint amount of blend to occur as some heat (very little) makes A/C work (feel) better as it dry's the moisture in the air. the door does the reverse for the heater system as the air gets too dry when moisture isn't permitted in. Thank you very much, guys! Cheers! :-)

[@Tundralifted]

Love this video, I’m going to look into when ford stopped using vacuum assist for their HVAC system.

[@63256325N]

Now that is one heck of a core price. Definitely want to turn that in unmolested....Thanks for the video.

[@tagjr9744]

I replaced mine (orings) a few days ago. It works perfectly.

[@donnierobertson3088]

Great job again like always

[@whitetiger8652]

Nice job Eric!

[@lilgamerboy6290]

Great diag! Thanks for sharing!

[@SmittySmithsonite]

Another system Ford cheaped out on in the later years of these cars. I'm still running the OE manual HVAC vacuum operated unit in our '86 Grand Marquis, and haven't had a problem yet! 32 years and 249k miles. Only vacuum related issues I had were deteriorating hoses (made it 20 years though!), a bad check valve, and a failed diaphragm in the parking brake release servo. Ended up just finding a NOS servo, and finally got that fixed. Also fixed the burned out BRAKE light bulb - I drove 7 miles at 65 MPH with the e-brake on recently! Talk about being mad!! That was the motivation I needed to get it done. It's nice when the parking brake releases itself when you put it in drive! Saves me the effort or reaching down with my short, stubby arms, HAHAHA! :D Guess that's how I formed a beer gut ... Hope you and the family had a great Thanksgiving!

[@bastianfromkwhbsn8498]

Sad but true. Had a 1997 Crown Vic with 150k+ miles on it which felt like a tank. Replaced it with a 2005 Grand Marquis because I got it cheap from an old bloke. It only has 30k miles on it and the interior feels more tired than the one in my old Crown Vic did, the materials are so damn cheap, unbelieveable.

[@PineHollowAutoDiagnostics]

Original vacuum HVAC system works fine too in my '96 Mystique! Although I personally prefer old-school cables and sliders :)

[@SmittySmithsonite]

You and me both, Ivan! No vacuum leaks with cables. :D

[@snakeskinproductions7500]

Yep. I've done the o ring swap myself on a family members car and of course it was in the 2% of ones that did not work 100%. It is better but still not a "confirmed fix". I gave it a shot because she is on a fixed income and as you know these units are pricey. Only had my time and a few bucks worth of o rings so what the heck. As I said she is a family member and elderly to boot so I came out of pocket and got her a new (remaned) control unit. as always thanks for the video's and remember, If you can do it, I can do it....

[@klwthe3rd]

Snake Skin Productions you keep saying it. But I CAN'T DO IT! That's why I have to watch SMA. Lol

[@rtchrg440]

$230 core charge! WOW! Great video Eric -

[@TheMadSciencetist]

Man, you my favorite digital mechanic. Ever thought of doing an on site series. I have a Titan that needs a blend door actuator replaced. It is a serious pain...anyways carry on and keep fighting the good fight

[@testosteroneinc.3800]

150 views in 3 minutes, yup Mr O has gone Hollywood 😁

[@Txcowboy80]

Refried Beans ...Dr.O

[@mr__No]

100k subs and no party!?!? Come aaahn mr O! :/

[@hidros1461]

On the road to 600k now! Crazy

[@bronzechicken4437]

I know the solution to this hands down, but it's worth the watch still since you learn about the system.

[@lvsqcsl]

It could have been worse. I had the plastic hinge break on the floor/defrost baffle and had to replace the whole duct assembly. The vacuum motors at the bottom were fine. Great video!

[@baxrok2.]

Took care of that all zippy zap like! Great info. Thanks!

[@scowell]

Great video... subbed. They definitely make it so it's not worth your money to tear the unit open... the core price is gonna drive up the junkyard prices too. Don't get me started on '90s Taurus VAPS or blower motor speed control... enough to say that when I sold the Taurus there was a blower speed switch in the glovebox.

[@johnlyons229]

eXACTLY what I needed. Thanks,

[@ojjenkins7110]

GOOD INFO ERIC. HOPE YOUR TG WAS A GOOD ONE. MERRY CHRISTMAS

[@100SteveB]

Mk2 Mondeos used a vacuum system, and they had a habit of getting stuck on defrost. The silicon rubber seals inside the switches used to age and turn into a sticky goo that would work it's way down the vacuum pipes and block them up. I had a few do that.

[@patrickmorrissey2271]

Very good video. I've heard those are tricky, but that explanation actually made total sense to me.... Find which funnel to stick your head in! Haha! Very nice.

[@rrmech11]

Nice job

[@kurtb6803]

If you take the HVAC unit apart, there are 4 or 5 barrels in there. Where the barrels connect there are little black o-rings which tend to go bad. If you are mechanically inclined you can just replace those yourself for a couple dollars.

[@klwthe3rd]

Kurt B Where do you buy the oem O rings?

[@kurtb6803]

Kenneth White just from a local hardware business. Just brought the old o-rings along to match the size.

[@klwthe3rd]

Kurt B Thank u

[@kameronstout4847]

My 94 F150 did the same thing the vacuum hose was broken under the hood I just slipped some hose over it works awesome now

[@OneAuto]

OK OK back the truck up......You have a vacuum operated Parking Brake Release Actuator!!?? Oh boy, learning something new again 👍

[@SmittySmithsonite]

The Crown Vics, Grand Marquis, and Town Car all had those (even a few GM vehicles did too). Not every model did though - I think it was an option. My first '86 Grand Marquis didn't have the servo on the parking brake assembly, or a vacuum switch on the shifter column.

[@JSchrumm]

Yes because a spring would be too technical.

[@chrisfreemesser5707]

My '77 Mercury Monarch had a vacuum-operated parking brake as well. Dunno if the Crown Vic/Grand Marquis did this too, but as soon as you put the car into gear the vacuum system would release the parking brake automatically.

[@JSchrumm]

Yes because a red light and a lever were too complicated..

[@thetinpin]

_"Yes because a red light and a lever were too complicated.."_ It functioned and was designed _exactly_ like every other standard issue cable/lock/spring type parking brake, including the little red light. If the auto release quit working, _it wouldn't affect brake functionality whatsoever._ I don't know about you, but I wish there were _more_ features that worked like that - If it works, great! If it's broken, who cares? You wouldn't even be able to tell it's there because it's a zero consequence failure.

[@davidn1562]

Awesome video at over 162K my 2002 GM just started acting up with the same thing.

[@mauriciodiaz6890]

Excelente video saludos desde chile

[@patricksterling7389]

Thanks. Mine works fine but good to know what to do just in case.

[@donnierobertson3088]

Another A+

[@denniswilkinson1118]

Very good.

[@HUBBABUBBADOOPYDOOP]

You make installation of rubber exhaust hangers easier with a spritz of brake parts cleaner... I wonder if it would rejuvenate the diaphragms in the HAVC Programmer Module? My '89 Reatta uses the vacuum system, too. Same color vinyl hoses, the '88-'89 Programmer is a small box, behind the glove box, between the ECM and BCM. The '90-'91 Reatta is in the dash like this Vic. My '77 Cutlass had a similar vacuum system, as many cars did/still do. I think they are pretty reliable, and simple to service; on some models- the actuators are inaccessible unless the dash is removed. Why don't you like the system? I do admit- nothing beats a lever and cable control... the good 'ol days!

[@samrugtiv5563]

good job Eric, that is the right short cut you have done.very well done. thanks sam

[@windynabbie]

Had the same problem on a 01 Ram Van never did figure it out, wish I saw this video a few years ago

[@R.E.HILL_]

Nice one... I wish for a 5.6 or 6.7l engine swap for Christmas present. You know a 5 part long one. Looooong time since the last one...

[@mr.h4714]

Great stuff from SMA, as usual.... Bag any noteworthy bucks yet this year???

[@graymodeler]

I had this problem on my 84 Z28. It would hiss until it warmed up, then seal. I he selector wheel had a broken clip letting in air. I used a screw to Replace the clip. My Mom had a78 T-Bird that had the vac light covers, and the E brake that came off when you put it in drive.

[@drfalcon4102]

You posted this at a good time, at hosptal with a sick wife, and shes finally sleeping, good morning

[@SmittySmithsonite]

drfalcon4102, hope your wife gets better soon. God bless.

[@drfalcon4102]

Thanks guys, she had surgery and is doing great

[@wyattoneable]

Interesting design. I'm impressed the owner even worried about it. Heat coming out of anywhere and most Hillbillies around here wold say "good enough" ! I hope your family had a great Thanksgiving.

[@DriveShaftDrew]

good job buddy

[@Gears.and.Gadgets]

I remember those being no longer made. And no longer available. Where did you find a rebuild unit. All I've found is rebuild services for them.

[@Giggiyygoo]

I had no idea a car of that year would have all those vacuum controls. Learn something new every day.

[@thetinpin]

Yup. My 1986 Grand Marquis and 1987 and 1988 Town Cars were set up exactly the same way that my (current) 2009 Crown Vic is.

[@SmittySmithsonite]

They've been using vacuum for controls for over 50 years. Some of the old timers had vacuum WIPER motors! On the opposite end of pneumatics, I drove a tractor trailer that had an air-operated starter. That one was fun when you had multiple air leaks in the brake system ...

[@Giggiyygoo]

Smitty Smithsonite I remember the older corvettes had vacuum pop up headlights, I just thought all that stuff stopped sometime in the 80s

[@jeffr0]

Not surprised to see old tech in a recent vehicle. Ford made this car (and the Crown Vic) EXACTLY the same for about 10 years, including stereos and A/C. That’s how you could could buy one for a song - no retooling.

[@khakiswag]

Those panther platform cars were on the market for decades. Although the car is fairly new the technology behind it not so much. The last complete redesign was in the early 90's when the OHC Modular engine was introduced. It's 20 year old technology is one of the reasons they are so reliable.

[@kennethhudson8013]

Damn, I wish you were my mechanic!

[@litchar]

You would like to have a mechanic that would charge you $600 for a $15 fix just because it has a warranty for the mechanic? Yes if the new control unit when bad you wouldn't be on the hook for the cost of a new one but you would still have to pay your "mechanic" to put the replacement in when he should have just fixed the old one with a dollar worth of O rings in the first place and saved yourself $600

[@rickuyeda4818]

My '96 Dodge Ram had the same problem. It was a cracked vacuum line on the firewall. Easy fix.

[@jimbola77]

good job partner!!! so the control module was fried???? thank you for sharing God Bless.

[@jasonsage1404]

Hey buddy thanks for the solution to fix this on '02 F150 Supercrew. Now maybe there is an easy fix for my temp control issue now, bought brand new OEM blend door actuator and put in a new blend door but I have very limited temp control range such as all the way cold and maybe a few temp degree increases such as 70, 75 and 80 is all the way hot and it should be all the way hot at 90* I tried recalibrating the EATC and didnt seem to do anything and there isnt any codes....

[@mindthependulum6245]

So, to speed things up, if I test the vacuum connections as good, then just replace the HVAC head unit?

[@Reaglesracing44_]

on my 02 mercury car what causes the turn signals to blink fast,normal,fast? i was told it may be the switch or the light module

[@FABAutomotiveDetailing]

Man I wish my customers kept their car floors that clean! We have refused under dash work before because the floors were so nasty. Great informative video!

[@thetinpin]

Really? _That_ bad? Damn! Leaky windshield => carpet mold issues or something?

[@FABAutomotiveDetailing]

tin pin yes! We had one come in one time that had half eaten cheeseburgers, misc foods, cigarette butts, spoiled milk and trash all over the floors. You couldn’t even see the floors. Normally we just lay a fender towel down on dirty floors then go to work. This one was terrible and smelled awful. I don’t know how people drive something like that and not be embarrassed.

[@testosteroneinc.3800]

Webster Slaughter Then I would be a perfect customer to you! I dont eat in any of my cars. My OCD will make me pull over and pick lint out of the carpet. Dry Texas air, means no rust or mildew issues. Our wiper blades and door seals sure dry out fast though... 😒

[@Bereft777]

Webster Slaughter drive either a Marquis or crown Victoria and you'll want to keep it clean. Such a great vehicle!

[@FABAutomotiveDetailing]

Refried Beans you are my kind of person! I am the same way about my vehicles. My kids hate it but will thank me one day.

[@waltershulas623]

Hey Eric great video is that a dorman unit

[@Tallguy203]

Eric, do you still have the amazon store? Tried a couple times to look for a light and couldn’t get on the sight.

[@SVTJD]

I refurbished my eatc unit myself. Replaced all the o-rings internally and only spent $13 and did it in an hour. DONT GET ROBBED BY A MECHANIC THAT WANTS YOUR MONEY. It wasn’t hard, don’t be afraid.

[@aussiebloke609]

And this is why I still miss having a simple cable attaching to the blend door mechanism. And another cable for the heat. They rarely broke, were easy and cheap to fix, and are infinitely variable. I really haven't liked any system since...they don't really do anything different or better, and generally do somewhat less, and much worse...and for a much greater cost.

[@amtpdb1]

I have a 04 Lariat and with the air on low sometimes driving down the road the fan goes to high speed. Where would you start?

[@Brian-cr6rb]

Didn't read all the comments, but there's gotta be a way to dicker the head unit to fix it's fault! I'd play Frankenstein to try to fix it. You should try it and show it. But the damn thing has quite the core as you said. I hate the fact that parts are designed to fail!

[@Apathetik]

If you have a good size leak auto brake release , or the intake manifold , or if your ford is old enough trans shift control system that same problem can happen.also a leak in the power brake system.

[@ozzstars_cars]

The Grand Marquis is a very popular car at the senior center where I go to play bingo on Tuesday afternoons.

[@jamesmcqueen2618]

Great video and a great repairman also. Wish you liver close to me.

[@davids8956]

Nice, 2007 and it still came with a cassette player.

[@jhuntosgarage]

Same for 1999 Chevy Suburban for vacuum principles or are they all electronic? Thanks for sharing!

[@SouthMainAuto]

They are all electronic I believe

[@jhuntosgarage]

South Main Auto Repair I believe you are correct. Thanks again.

[@sweetwilliam49]

What was wrong with the old wire on a lever trick

[@droontop]

Hey, I got a 2005 Grand Marquis and the heater doesnt work in the car. Whenever you switch from cold to hot, the dial just keep spinning as if it not attached from the inside. AC work great jus no heat, any suggestions ???

[@InternetDude]

If you put in silicone O rings it would be good for the life of the car. Doing it your way means more $$ for you in the long run when the aftermarket one leaks again down the road. The key here is silicone.

[@Reaglesracing44_]

they make rebuild kits for those hvac controller

[@elvismcgilvray]

If the vaccum line comes in at emergency brake which operates with vaccum so if a leak under hood would it effect emergency brake?

[@MichaelDoerner]

Completely unrelated comment to what your AWESOME video was about. Do oxygenated fuels (i.e. gasoline with 10% ethanol) throw off the long-term-fuel trims on a modern car? I just had a vacuum leak repaired, and the long-term fuel trims were still around +25%. I threw in some mid-grade gas later on, and the long-term fuel trims started going -10%. It might be because of computer re-learn, might be because I threw in non-bargain brand gas, might be because the engine was warm...dunno. However, I'd like to know if 10% ethanol gasoline would possibly cause a lean condition in the engine and positive long-term fuel trims. Thanks!

[@shadowdog500]

In about another 5 years the vacuum lines will start rotting out and leaking. I've had fun with these before. Chris

[@dukeman7595]

Loved the video, the part price is pricey.

[@teacherlynn671]

2000 Marquis air only comes through the vents. Any help would be thankful for Vacuum motors seem to be OK. ECC was rebuilt and was good when I sent it in I was told. Pleas help

[@zx8401ztv]

It's an odd way to control the heating/cooling but it does work, well if the seals in the controller are okie dokie :-D. If it was mine, i would pull the control unit to bits, i'm just a nosey git lol :-D

[@ronp1018]

I just replace the O-rings myself and saved $1000

[@ColinFisher]

I have a '96 Dodge Ram that does the same thing. I knew it was vacuum related but had no idea where to start troubleshooting.

[@ShainAndrews]

Not a lot of details to work with there. Engine? 4x4? Regardless start under the hood. On the top of the firewall there is a hard plastic vacuum line. This is just a land mark for you to find a vacuum line. Now follow it to the passenger side. At one point it goes through the firewall into the cabin. If you have 4x4 it will also T off and go down to the front CAD (central axle disconnect). The drop down to the CAD is prone to breaking with age. If you don't see any issues there, turn tail and follow the line back across to the driver side firewall. Follow all the lines until you see where it connects to the engine that is the second most common failure point. Personally I rip all that brittle hard line out and replace with silicone tubing that can be had from McMaster, or you can get rubber line from the parts store... or you can get the hard line from the parts store too.

[@ColinFisher]

Shain Andrews Thank you for the information. I'll follow your instructions. BTW it's a 4X4 , 360 CI. 68K original miles.

[@ShainAndrews]

Anytime. Just roam around under the hood you will find it. 68k miles? Goodness take the old girl out on the town a little more often ;-)

[@Apathetik]

My truck 1995 f 150 it was an intake manifold internal leak.

[@rimmersbryggeri]

They use vacuum because they have changed very little since 1953. Do they still operate the windows by vacuum aswell?

[@FourSeasonsNorth4x4]

Vacuum actuator park brake? Is my hearing faulty? Curious now. 👍👍 Poops, there it is....”hey dude, there’s your problem..not your hearing but your eyesight!!” LoL 😂

[@thetinpin]

Been there, fixed that system. I've never had to replace the control unit however on any of my Panther body Fords: 1986 Mercury Grand Marquis 1987 Lincoln Town Car 1988 Lincoln Town Car 1994 Lincoln Town Car 1998 Lincoln Town Car 2000 Lincoln Town Car and my current 2009 Ford Crown Vic ... all use an (almost) identical vacuum actuated HVAC configuration. I suspect the 1998 Explorer 302w Eddie Bauer my mom had was vacuum controlled, but it never broke in the 10 years she had it. The automatic climate control designs throw a temperature sensor into the mix with that fancy digital display. Off the top of my head, I can't remember if it's only the automatic analog (80's) and digital (90's+) systems that have that superfluous vacuum controlled auto parking brake release (shifting out of park to drive supplied vacuum to the release actuator and hiss to your ears) because that line always got the 'golf tee treatment' immediately after purchasing.

[@SmittySmithsonite]

The 80's Fords were built 10x stronger in every system compared to today's junk! Still haven't had an issue with our HVAC in the '86 Grand Marquis - 32 years, 249k miles so far.

[@thetinpin]

_"Still haven't had an issue with our HVAC in the '86 Grand Marquis"_ Holy crap! You must be a very lucky person! All 3 of my 80's Panthers had issues with a vacuum actuator in the dash. Each needed a vacuum actuator for the blend door (the 87 also needed the blend door return spring that pulled the door shut when there was no vacuum) and a preemptive complete vacuum line overhaul due to some lines becoming brittle and cracking over time. It wouldn't be a bad idea to get your hands on a Ford made "electrical and vacuum troubleshooting manual" like I did, just in case a befuddling problem shows up. They're fantastic and give you nicely detailed and *_super easy to read_* vacuum/electrical diagrams, as well as troubleshooting procedures for each and every system. They're very inexpensive for what you get too. They are specific to the year, so you don't have to worry about small year-to-year changes and colors being different. Here's yours: www.ebay.com/itm/1986-FORD-MERCURY-GRAND-MARQUISE-EVTM-ELECTRICAL-SHOP-SERVICE-MANUAL/360404659464?hash=item53e9caad08:m:mX5H3xq9Acrb2wO5HvmQqqA&vxp=mtr ... and here's what you get: www.justanswer.com/uploads/babarche/2008-11-09_023335_ATCvacuum1.jpg and www.justanswer.com/uploads/babarche/2008-11-09_024432_Ford_ATC_diagram_small.GIF

[@thehemiolds455]

Its that Dorman 🤔🤔🤔 😀😀😀😀

[@MrSlicer2424]

My 2003 grand maquis A/C switches from vent to floor/defrost under acceleration. Then back to vent. I've seen remanufactured control units on ebay for $120. Should I take the risk?

[@dennisstanbrosaerialphotos3270]

What ended up fixing your issue? I have same issue. Thanks

[@MrSlicer2424]

@dennisstanbrosaerialphotos3270 I ordered a remanufacturer head unit . Easy 10 min installation !!

[@fredflagstone9467]

Here in Phoenix, defrost is all you need, and that's only for two or three months. It would be the perfect "broken condition" around here.

[@johneaston4963]

Fordtecmakuloco has a video how to repair them,

[@ShainAndrews]

kzbin.info/www/bejne/hqXJppaElpuFldE

[@fritz614]

I do not even have a car with this actuator and never will, why did I just spend 15 mins how to change the o-rings!!! Love KZbin!

[@sanity1977]

“O” rings....

[@testosteroneinc.3800]

James Fritz Cause the O'ster is the best! Always entertaining to watch a master work, regardless of make or model

[@TheCarterHour]

But my video was the original on how to fix a Ford EATC. :) Plus the list of parts you need. Cheers kzbin.info/www/bejne/a3rWdaZjg5agrKc