(2nd Generation) FAQ: Help! My HVAC is cold on one side, hot on the other!

[digitaloutsider]

I wrote this for the RegalGS forums, but I decided to post it here too since it applies to most any dual climate control W-bodies. Note that on the first-gen Regals with DCC, the problem is most likely the control unit, not the actuator.

 

 

 

How to fix your dual climate control:

 

Before you take your vehicle into the stealership and bend over to take it up the ass on their part and labor prices, there's a good chance that you can fix the mysterious hot-on-one-side-cold-on-the-other problem that plagues our digital electronic HVAC systems.

The problem can be caused by one of two things:

 

The HVAC control module itself

 

or

The left/right side door actuator

 

 

 

There's a very good chance it's the simpler, more affordable actuator. It's a black electronic module manufactured by CEI. It's entire job is basically to turn a little white knob that controls the hot/cold door. In many instances, it will do it's job perfectly for many years until one day you're stuck with hot air on one side and cold air on the other.
 

 

Mysteriously enough, this problem came up for me right after I disconnected and reconnected the battery. GM says that this can cause the HVAC control module to fail to initialize the door position properly, and will thereby need to be replaced (at the tune of around $500). I did a little searching around on this forum and found that ss4ever had the exact same problem I did, right down to the affected side.
 

 

I deciced to disassemble the car and find the problem.
 

 

 

 

This is what you see with the glove box removed. To remove the glove box, first take off the passenger side insulator located at the bottom of the instrument panel. It's held on with three christmas tree-type clips. Once it's off and out of the way, remove the three 7mm (9/32) bolts and finagle the box out of the compartment. The actuator is the black box with the white sticker that has an "R" on it. It's held on with what I believe are two 6mm screws.
 

 

 

 

The actuator unit.
 

 

 

 

Here is the unit with the cover removed. It now becomes apparent what the problem is. The larger gear that turns the knob is made of a cheap plastic that is put under an immense amount of force. It simply can't take this pressure and will finally give out eventually. This isn't a matter of "if", it's a matter of "when". If this is what your actuator looks like, you've found the problem. The part number for this unit is 16163982. It's kind of pathetic to pay nearly $100 (GMPD) for what essentually is just a small plastic gear, but this is what GM has given us. There is, of course, always Ed Morad.
 

 

I'll be heading to the junkyard as soon as I can to see if any other GM vehicles use this module (cheaper alternative to GMPD or Ed Morad). I'm assuming any dual climate control car will use this, but knowing GM, each model is probably different in some respect. I DO KNOW that the Grand Prix/Regal units are interchangeable.

[GP1138]

Very nice!

[IRONDOG442]

The Intrigue is exactly the same the passenger side blows ice cold and the drivers side blows warm. make this a sticky or something a very useful guide for a very common problem.

[marcusa]

My Intrigue had the opposite, when on Heat Drivers Side was COLD and passenger side was hot, down to the two vents in the middle. The problem was my Low Blower fuse was blown. Hence, it is wise to check all HVAC and Blower fuses beforehand

[Guest TurboSedan]

my Regal has exactly the same problem. passenger side stayed hot and driver's side would go from hot to just warm. i took the actuators out and BOTH of them had cracked gears inside

 

thankfully i could operate the doors by hand so i wasn't stuck with hot air during the summer. now that it's getting down into the 30s at night i need to manually move the doors again to allow heat in.

 

did you ever get replacement actuators Shaun? thanks for the write-up! i wouldn't have even attempted removing the actuators without it.

[Pontiac6KSTEAWD]

This is coming from way out in left feild, but hear me out...

 

That unit, is also used on the 88-92 Eagle Premier. But on the eagle, its used as a blend door. Which I guess is the same thing really. Which isnt to far off base if you think about it, since the Eagle Premier is built by like 7 different car companys. Also a Jeep dealer will have it for about 70 bucks (a hell of a lot cheaper than the GMPD). I would at least experiment with it for the cost diference. If you can find one in a junkyard, check it out. If the car has a center console, it is right in front of the center console facing up. If no center console, which means it will also be easier to work on, its over the tunnel right by the firewall facing up. The back screw on those things are a bitch to get at... Let me know If I am seeing things, but i dont think I am. It has the same plug, the same internal parts, im telling ya, its the same thing.

[slick]

Any updates Shaun?

[BCM]

Well...at first mine just started blowing hot air out of the passenger vents, then through all of them(on any temp setting). So I got to work and this is what I discovered

 

 

 

 

i searched that part number on gmpartsdirect.com and it says not found?

 

I turned it by hand, now the passenger side blows COLD air, but the drivers side just blows air, not hot, not cold....Is there another one of these on the driver side?

[Pontiac6KSTEAWD]

Tellin ya man, try to compare the same part, but at a dodge dealer for a 90 eagle premier. Its the same part I am ALMOST positive..

[shyguy164]

I had this exact problem on my 95 cutty convertible with the dual auto climate control. The driver side went from cold to hot just fine. The passenger side stayed somewhere in the middle. Never all cold and never all hot. I found out it was the passenger damper motor. I ordered one from somewhere and it had the wrong connector on it. I went to the local GM dealership and they were able to find the correct part. The part # on the broken actuator is no longer valid. I think the dealership wanted like $100 or something, which I was more than willing to pay since I couldn't seem to find the correct one on my own.

[digitaloutsider]

Tellin ya man, try to compare the same part, but at a dodge dealer for a 90 eagle premier. Its the same part I am ALMOST positive..

 

The pre-97 W-body ones don't work. I HIGHLY doubt a dodge part will.

I turned it by hand, now the passenger side blows COLD air, but the drivers side just blows air, not hot, not cold....Is there another one of these on the driver side?

 

Yes, the driver's side has one too.

[GtipGary]

Yeah the Gtip is having the exact same problem... blowing warm out of the passenger side... someone told me it was something under the dash that controlled this... maybe ill rip the damn dash apart tomorrow and see if i can find it

[shyguy164]

Yeah the Gtip is having the exact same problem... blowing warm out of the passenger side... someone told me it was something under the dash that controlled this... maybe ill rip the damn dash apart tomorrow and see if i can find it

 

You shouldn't have to tear much apart. I got at it from the passenger kick plate/sound damper thingy underneath the dash.

[Casey]

M-kay...my pass. side hot/cold diverter door actuator ('96 CS) wasn't working, so after reading the above I figured it was the white gear- nope. Mine was fully intact. I grabbed another pass. side actuator from the salvage yard, inspected it inside (gears good), tired it out, and still no worky. How does one verify there's power to the actuators, or which terminals on the connectors should have power? I have a voltage tester, but no service manual yet...

 

The vac lines and HVAC controller thingy behind the glovebox are all functioning- the system switches between Upper/Lower/Etc. just fine, so I am doubting it's the main dash control unit at this point that's teh problem.

 

How does one test that the PASS control button is functioning and exactly what is controlled when the PASS button is depressed (i.e., turned on)? Does the pass. armrest temp control rheostat switch control the pass. side tempertaure by itself once the PASS button is depressed?

 

I also have a non-functioning A/C compressor clutch, but I'm not sure if that's an related problem or not. It doesn't turn on with either dash HVAC control unit I have.

 

Casey

[slick]

Rachel's Regal is having the hot/cold fun as well. As Casey is saying, if it's not the broken gears, then what? Bad HVAC unit?

[GtipGary]

yeah mine has the hot cold deal and it wasnt the gear being broken. Im still confused!! Also for some reason last winter it took ungodly long for my heat to get warm and when it did it wasnt very warm... now it doesnt work at all.

[Casey]

yeah mine has the hot cold deal and it wasnt the gear being broken. Im still confused!! Also for some reason last winter it took ungodly long for my heat to get warm and when it did it wasnt very warm... now it doesnt work at all.

 

The lack of heat could be a plugged heater core. Have you tried disconnecting the heater hoses at the firewall connections and flushing (and back-flushng) the heater core?

 

Reagrding the hot/cold issue, I'm guessing the acutators which control the driver and passenger side flapper doors are both directly controlled by the rheostat switch, with an override feature for the passenger side enabled by turning the PASS switch on and using the pass. door rheostat to control pass. side temp. I don't see a heater valve anywhere, either, so for now, I'm also guessing warm coolant is always flowing through the heater core.

[GtipGary]

No i havent really tried anything because up until the past few days it hasnt been cold. But when you have a girl in your car at night time no matter how nice it is outside they think its cold. So the ex tried turnin on the heat and it wouldnt work. I should probably try to figure it out before 60 turns to 10 or below.

[Casey]

After reading this tip on another forum, I thought it might be worth sharing. If your car's battery has recently been replaced or disconnected, the Climate Control unit may have forgotten the position(s) the actuators were in prior to battery disconnect. The suggestion was to disconnect the battery for ten minues, reconnect, then turn the CC unit to max cool on both sides to "re-set" the actuator door postions.

 

I have no idea if this works or not, but my battery was recently replaced, so it may be worth a try on my part. I will report back with what I find, if anything.

[Casey]

That didn't work.

 

I am seriously considering switching to the standard HVAC system. With no way to test the actuators, I'm not sure what else to try with the dual zone setup.

 

Does anyone know (or has someone here done it?) what's involved in switching over from the dual zone to the standard HVAC system?

[digitaloutsider]

If the actuators are "out of range" (i.e. sending a variable back to the control unit that's too high or low), it won't work. This is a problem with the older ECC units. You may want to grab a new one out of the yard and see if that fixes anything.

[GtipGary]

I dont have the dual climate control but neither my a/c or my heat work ... ill have to try to figure out what it is.

[Casey]

If the actuators are "out of range" (i.e. sending a variable back to the control unit that's too high or low), it won't work. This is a problem with the older ECC units. You may want to grab a new one out of the yard and see if that fixes anything.

 

Which year(s) ECC units will work on my '96 and/or which year(s) are considered "older"? I checked out a few different year W-bodies at the salvage yard and a few listed on eBay to compare to mine, and it looks like only '95-'97 will work...or will other '98 and up ECCs work, too?

[digitaloutsider]

'95-97 CS only.

[GtipGary]

Any good ideas as to why my godforsaken heat doesnt work?