86 Heater Control gone WACO
Thread Starter
Instructor
Joined: Oct 2006
Posts: 246
Likes: 2
From: Elk Plain WA
St. Jude Donor '11
86 Heater Control gone WACO
Fall is in full force now so I have need for heat. I have the "automatic" version of the controls. First time I turned set the heat controls on I noticed that the engine warmed as usual, but the air continued blowing cold. Then suddenly the heat came on full force and I could not shut it off. Doesn't matter what control buttons you set she pumps heat once it starts to work.
BTW: My AC hasn't worked for a couple years but this heat control issue just started.
Any ideas?
Thanks
Tom
BTW: My AC hasn't worked for a couple years but this heat control issue just started.
Any ideas?
Thanks
Tom
Team Owner
Joined: Jan 2003
Posts: 20,306
Likes: 242
From: Summerland B.C. Canada
Sounds like the blend door is stuck on full heat. Could be a bad motor or broken clip between motor and rod or rod and door. The 86 has a water control valve that is operated by vacuum, so that would have to be stuck open, also.
If you remove the blower control module from housing and look inside, you should see the door moving from one side to the other, when the temp is switched from cold to hot, while in auto mode.
Here is some info from my 86 FSM
http://members.shaw.ca/dankai/HVAV'S.pdf
http://members.shaw.ca/dankai/HVAC%20Electrical.pdf
Here are some pics from my heater core project, some show the motor, door and rod.
http://members.shaw.ca/dankai/Heater%20Core%201/
If you remove the blower control module from housing and look inside, you should see the door moving from one side to the other, when the temp is switched from cold to hot, while in auto mode.
Here is some info from my 86 FSM
http://members.shaw.ca/dankai/HVAV'S.pdf
http://members.shaw.ca/dankai/HVAC%20Electrical.pdf
Here are some pics from my heater core project, some show the motor, door and rod.
http://members.shaw.ca/dankai/Heater%20Core%201/
Drifting
Joined: Aug 2006
Posts: 1,624
Likes: 2
From: Canandaigua New York
There is another possibility as well.
My CC would do the same thing and 'flake out' with the display going nuts.
I removed it and took the controller out of it's case.
There is a board that plugs in the back of the controller head.
Pull it out and clean the contacts real well. They get corroded over time.
Reassemble and reinstall.
I did this with mine and everything works fine now.
My CC would do the same thing and 'flake out' with the display going nuts.
I removed it and took the controller out of it's case.
There is a board that plugs in the back of the controller head.
Pull it out and clean the contacts real well. They get corroded over time.
Reassemble and reinstall.
I did this with mine and everything works fine now.
Thread Starter
Instructor
Joined: Oct 2006
Posts: 246
Likes: 2
From: Elk Plain WA
St. Jude Donor '11
Fixed (was electrical problem)
I decided to go for the electrical first, so I removed the control unit from the dash to check it out. No apparent corrosion at all. However, when all put back together the HVAC controls are functional again. Must have been weak/dirty contacts on either the main connector or the PCB. 
Last edited by tdf; Oct 30, 2010 at 12:03 PM. Reason: spelling
Drifting
Joined: Aug 2006
Posts: 1,624
Likes: 2
From: Canandaigua New York
Did you remove the control head from it's case?
The contacts between the front head and board are what I found
to be dirty and corroded somewhat.
Sometimes you really don't see the oxidation. It may 'look' clean, but there could be
a very thin film on the contacts. It's better to clean them with a little emery so you don't
have to take it apart later on.
I'm glad it's working for you.
The contacts between the front head and board are what I found
to be dirty and corroded somewhat.
Sometimes you really don't see the oxidation. It may 'look' clean, but there could be
a very thin film on the contacts. It's better to clean them with a little emery so you don't
have to take it apart later on.
I'm glad it's working for you.
Thread Starter
Instructor
Joined: Oct 2006
Posts: 246
Likes: 2
From: Elk Plain WA
St. Jude Donor '11
Yes - Removed from Box
Keystring.....Yes to your question. That's why I mentioned the PCB connector. I pulled the PCB out of the box and cleaned those contacts as well. Used spray electical cleaner and a soft cloth. Hopefully that takes care of the issue for a while anyway.
Drifting
Joined: Aug 2006
Posts: 1,624
Likes: 2
From: Canandaigua New York
I haven't had anymore problems with mine either.
Makes you wonder how many have sent theirs out to be repaired when it was probably just dirty contacts.
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Thread Starter
Instructor
Joined: Oct 2006
Posts: 246
Likes: 2
From: Elk Plain WA
St. Jude Donor '11
The Grimlins are back! I was afraid of that. This time I do have the ability to cycle the blower off and on, so cleaning the ICBs did improve the elctrical side of things. With more driving time I now know that a door is sticking somewhere inside the heater internals. If the heat won't come on (this is gonna sound weird, I know) I can make a sharp brisk right turn and hear a door go "plop" and I instantly have heat. So I need to get inside and see whats sticking and why....Grrrr
Le Mans Master
Joined: Sep 2006
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Sometimes the rubber seal is affected by smog and age and softens. Then it makes a really GOOD seal. Try putting armor-all on the seal to slicken it up.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
From your description it sounds like your good electrically now it seems you just have a mechanical problem (loose actuator, loose rod, broken plastic clip for the rod, blend door hinge issue) with the blend door function. Pull the passenger side knee bolster/hush panel and have someone work the AC/heater controls to adjust the blend door open/closed so you can see what is what.
Thread Starter
Instructor
Joined: Oct 2006
Posts: 246
Likes: 2
From: Elk Plain WA
St. Jude Donor '11
Blend Door Rod Clip
From your description it sounds like your good electrically now it seems you just have a mechanical problem (loose actuator, loose rod, broken plastic clip for the rod, blend door hinge issue) with the blend door function. Pull the passenger side knee bolster/hush panel and have someone work the AC/heater controls to adjust the blend door open/closed so you can see what is what.Agent 86 and engle1147....you were correct! The clip that holds the rod for the blend door to the actuator motor arm is missing! I found what looks like it might be 1/2 of the plastic clip on the floor. Is that clip a white colored clip? I was able to see that the acuator motor is working (moving the lever when changing the heat setting on the control panel). Just got to get a replacement for that clip or make a mechanical connection between the arm and the rod some other way.
I wonder if GM has that clip?
Thanks for the Tips Guys
Last edited by tdf; Feb 27, 2011 at 08:23 PM.
Thread Starter
Instructor
Joined: Oct 2006
Posts: 246
Likes: 2
From: Elk Plain WA
St. Jude Donor '11
My Own Solution - Actuator Re-Attachment
After finding that the plastic clip was a discontinued part I decided to come up with my own solution.
The blend door rod is threaded 10-24 (figured out by trying nuts on it until the threads matched). Starting with a 1/2 inch by 1/2 inch aluminum bar, I cut a short piece and drilled and tapped one end 10-24 to thread. That side will attach to the rod threaded to it. On a perpendicular side I tapped a M6 x 1.00 thread hole to take a bolt for connection to the motor lever arm. With the bolt bottomed out it should be locked in for good. I don't think I will need worry about the connection anymore. :-)
The blend door rod is threaded 10-24 (figured out by trying nuts on it until the threads matched). Starting with a 1/2 inch by 1/2 inch aluminum bar, I cut a short piece and drilled and tapped one end 10-24 to thread. That side will attach to the rod threaded to it. On a perpendicular side I tapped a M6 x 1.00 thread hole to take a bolt for connection to the motor lever arm. With the bolt bottomed out it should be locked in for good. I don't think I will need worry about the connection anymore. :-)
