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'90 A/C problem


Guest slwalton72

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Guest slwalton72

I know the AC works and blows cold. However it stays stuck on Heat. The system turns off and oen fine, defrost front and rear work, you get vent air, just when you turn on the AC it stays on heat...... .

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Guest slwalton72

Thats did the trick, im back on my ac. I guess the motor went out cause it would switch when I got it, thnx.

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Guest slwalton72

TY Barney, I was curious about that. When I got the car it worked when it wanted to, then one day it just stayed stuck on heat. The ac blowd damn cold in the car. Im going by pick-a-part today, so hopefully I will run across one. I've had the car for a couple of years and it has sat for most of it. Last summer I installed a new alternator, harmonic balancer, cps, csps, icm, coil, plugs & wires. Then it has sat til now. I have a renrwed interest in cleaning the car up and making me a toy out of it, so Im sure you guyd will be hearing from me more.

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Guest slwalton72

Question though cause I went out there and played with it again. The controller works when I use the the buttons to shift it thru its various function, it just won't shift the dampner motor from a/c to heat which is what makes me think the motor is out. My tbinking is just telling me that if it was the controller it wouldn't do anything but stay stuck on one function not allowing you to turn the ac on and off, fan motor, defrost ect....When I hit the button to turn on heat the ac shuts down, but of course you dont get any heat cause it doesnt actuate the flapper /dampner.

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Guest slwalton72

Ok, when I turn everything off it turns off, if I put it on auto it blows cold top, push bi-level it comes out top and bottom, push defrost and it blows out by the windshield, I turn it on heat and nothing. Now if I shift the actuator rod behind the glove box manually i get hot air and no ac. All the lights work on the controller and fan works thru all stages the way it should. This is why I think the actuator motor is whats bad.

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Guest Mc_Reatta

You seem to be confusing the CC head unit with the HVAC Control Module.

The head unit is in the dash and has all the buttons and display and the computer that operates most of the climate control system.

The Control Module sits behind the glove box and contains the vacuum valves that open and close the vents that direct the air flow in the cabin, and has the motor that operates the blend door that controls the ratio of cooled air vs heated air. These blend doors tend to gum up a bit and stick if they aren't used much as you seem to be experiencing. The motor that moves the door is very slow and weak as designed and sometimes can't budge a sticky door.

First thing I wound suggest is to pull the glove box and find the HVAC Control Module. At the top you will see the white plastic rod that goes to the blend door, and where it simply clips to the lever arm that is attached to the motor.

Unclip this rod and move it left to right and feel how much resistance there is especially at both ends. With the rod still disconnected, start the car and turn on the AC. Adjust the head unit to command max heat and observe the lever arm and the motor the lever should move to the right. If it doesn't move or when it stops moving, command the system to max cool. The lever should now move to the left.

This will tell you if you the motor is working or the blend door is the problem.

If the motor doesn't work, just get a whole HVAC Controller unit and replace it.

If the motor works, you can try to lube the linkage to the blend door as best you can. (It's hard to get at.) and just move the rod from side to side and try to get the action to smooth out some so the motor is able to move it by itself again.

With the head unit still set to max cool and the rod disconnected, move the rod fully to the left and then clip the rod back onto the lever arm. As long as you don't turn the heat back on, you can ride this way all summer, even if you don't fix the issue, until you turn the heat back on.

There have been some good photos of this posted before. Check Ronnie's site and do a search and find them to help explain what I'm talking about.

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Guest slwalton72

No I'm not getting it confused. The motor thats behind the glove box is the one Im saying is not working. The blend and defrost work fine. Just if you want heat or a/c when you press the button the motor doesn't actuate, outside of that everything works fine and nothing is gummed up and moves freely.....

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No I'm not getting it confused. The motor thats behind the glove box is the one Im saying is not working. The blend and defrost work fine. Just if you want heat or a/c when you press the button the motor doesn't actuate, outside of that everything works fine and nothing is gummed up and moves freely.....
Mc_Reatta, Good information on checking the blend door motor. I just made a tutorial for ROJ with your instructions. I hope you approve. If you see changes that are needed let me know. HVAC Blend Door Motor Troubleshooting

EDIT: GOOD information, not God information as I originally posted. lol

Edited by Ronnie (see edit history)
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Guest Mc_Reatta

Ronnie, see if you can do a search and find some photos that were posted a good while back to go along with it.

Shawn, your post that indicated that you knew the difference didn't appear until after I was in the process of writing and posting my response.

The troubleshooting techniques were still valuable to know how to verify what is not working.

While the motor still might be available separately, it's not worth it. Just get a complete used controller and pop it in. They are very reliable items although I have had one vacuum valve stop working and of course it was the AC one.

Edited by Mc_Reatta (see edit history)
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Guest slwalton72

Trust me I appreciate the help from you guys. The knowledge shared here is priceless. I hope my response wasn't offensive as I honestly didn't intend it to be. Does anyone know of anyone who sells these or is this just a goodluck hunting it down item?

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