Manual Heater Temp Control inoperable
Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 838
Likes: 0
From: Member since May 99 (Before 99 CF Crash & Burn) Georgia
Manual Heater Temp Control inoperable
Found plenty about Automatic HVAC controls, but mine is manually controlled.
The car has not been driven for most of this year (I have been a caregiver out of state) but everything was fine in December 2011.
The car had a battery maintainer on it while it sat in the garage.
The heater blows cold air and the temperature control **** has no effect. A/C is cold (but 47* ambient temp today surely helped there).
Air outlet selector and fan work correctly.
What could it be other than the temperature control switch?
Is the manual HVAC control panel an all-in-one-box unit or three separate switches mounted in a panel?
Experiences, suggestions & WAGs welcomed.
The car has not been driven for most of this year (I have been a caregiver out of state) but everything was fine in December 2011.
The car had a battery maintainer on it while it sat in the garage.
The heater blows cold air and the temperature control **** has no effect. A/C is cold (but 47* ambient temp today surely helped there).
Air outlet selector and fan work correctly.
What could it be other than the temperature control switch?
Is the manual HVAC control panel an all-in-one-box unit or three separate switches mounted in a panel?
Experiences, suggestions & WAGs welcomed.
Team Owner
Joined: Jul 2006
Posts: 22,182
Likes: 4,178
From: Kannapolis NC
I'm not close to an expert on manual air/heat systems, but it sounds like your door that blends the air between heated and non heated is not moving to allow in the air that's passing over the heater core. Or possibly someone has blocked or bypassed the heater core so that the hot coolant doesn't pass through the core?
Last edited by 65GGvert; Dec 28, 2012 at 12:14 AM.
Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 838
Likes: 0
From: Member since May 99 (Before 99 CF Crash & Burn) Georgia
The fan and air outlet switches stopped working when I pulled fuse 18.
The outside air/recirculate switch stopped working when I pulled fuse 27.
The Temperature control still does not change the temperature from the heater.
<vent> And I have not been able to realign the fuse box cover enough to get the cover's screw to engage.
It would help if the top 20% of the fuse box was not underneath that flexible trim under the dash & I could see to get the top groove in the cover to align with the lip of the base.
</vent>
The outside air/recirculate switch stopped working when I pulled fuse 27.
The Temperature control still does not change the temperature from the heater.
<vent> And I have not been able to realign the fuse box cover enough to get the cover's screw to engage.
It would help if the top 20% of the fuse box was not underneath that flexible trim under the dash & I could see to get the top groove in the cover to align with the lip of the base.
</vent>
Last edited by Y-Body; Dec 28, 2012 at 06:14 PM. Reason: temp does NOT change
Burning Brakes
Joined: Mar 2011
Posts: 1,048
Likes: 5
From: Metairie LA
If your unit is truly "dead" you have a problem. The GM p/n is 10447750 and the Delco number is 15-72690. They are NLA from GM. I spent two days e-mailing and calling people and finally found a place in AZ that had two NOS. Paid $390.63. PM me if you want their information as they're not a vendor-maybe the other one is unsold. Only other option is used unit from a part out.
Team Owner
Joined: Jul 2006
Posts: 22,182
Likes: 4,178
From: Kannapolis NC
The fan and air outlet switches stopped working when I pulled fuse 18.
The outside air/recirculate switch stopped working when I pulled fuse 27.
The Temperature control still does change the temperature from the heater.
<vent> And I have not been able to realign the fuse box cover enough to get the cover's screw to engage.
It would help if the top 20% of the fuse box was not underneath that flexible trim under the dash & I could see to get the top groove in the cover to align with the lip of the base. </vent>
The outside air/recirculate switch stopped working when I pulled fuse 27.
The Temperature control still does change the temperature from the heater.
<vent> And I have not been able to realign the fuse box cover enough to get the cover's screw to engage.
It would help if the top 20% of the fuse box was not underneath that flexible trim under the dash & I could see to get the top groove in the cover to align with the lip of the base.
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Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 838
Likes: 0
From: Member since May 99 (Before 99 CF Crash & Burn) Georgia
I'll disconnect the battery tomorrow (& fight the cover again). There are no codes now.
Yeah, I was hoping to find more people who had already fought this particular battle.
I am wondering if the actuator (assuming that it has one as opposed to two for the dual systems) might be bad or has a bad vacuum line (again assuming there is a vacuum line to an actuator.)
Then again, it could be a bad dash control unit since apparently there are not three switches mounted on a panel (Ahhh, the good ol' days).
Burning Brakes
Joined: Mar 2011
Posts: 1,048
Likes: 5
From: Metairie LA
I've seen situations where the diverter door can stick due to age and the foam edge seal turning into mush, thereby sort of locking it in place. Determining that would require a fairly significant teardown. PM'd you on the information where I got my "new" part.
Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 838
Likes: 0
From: Member since May 99 (Before 99 CF Crash & Burn) Georgia
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Your SINGLE Actuator Controller is located on the left side of the air box. If you look under the drivers side dash on the side of the air box, you will see it:
Your single manual actuator is on the LEFT side circled in red. You will NOT have the one on the RIGHT circled in red.
Pretty simple:
Turn the controller fully HOT and fully COLD and see if the shaft that moves the door moves. If it doesnt move, see if you can hear the small electric motor inside the controller is running.. Here is what happens when the main gear cracks:
If its cracked, it will not move the damper temp control door
BC
Your single manual actuator is on the LEFT side circled in red. You will NOT have the one on the RIGHT circled in red.
Pretty simple:
Turn the controller fully HOT and fully COLD and see if the shaft that moves the door moves. If it doesnt move, see if you can hear the small electric motor inside the controller is running.. Here is what happens when the main gear cracks:
If its cracked, it will not move the damper temp control door
BC
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
IMPORTANT!!! Read the two test points on the top of fuse 18 to chassis ground with the ignition switch ON. Make SURE that you see FULL battery voltage on each test point.
That fuse is ppowered by the output of the ignition switch. A known failure item..
BC
That fuse is ppowered by the output of the ignition switch. A known failure item..
BC
Burning Brakes
Joined: Mar 2011
Posts: 1,048
Likes: 5
From: Metairie LA
Head Unit
Mine is a '99. Part number referenced is the correct one for your car.
Here's the parts blowup:
http://parts.nalleygmc.com/showAssem...roduct=2821101
#5 is the auto/dual zone controller and #11 is the manual unit. If you look closely, they are both the same (auto) p/n, which is impossible, since the two are not interchangeable. The research I did came up with the number I listed above, and the part I have in hand is a manual controller. FWIW.
Here's the parts blowup:
http://parts.nalleygmc.com/showAssem...roduct=2821101
#5 is the auto/dual zone controller and #11 is the manual unit. If you look closely, they are both the same (auto) p/n, which is impossible, since the two are not interchangeable. The research I did came up with the number I listed above, and the part I have in hand is a manual controller. FWIW.
Last edited by PhilsFRC; Dec 29, 2012 at 07:26 AM.
Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 838
Likes: 0
From: Member since May 99 (Before 99 CF Crash & Burn) Georgia
Minorl update
I can hear the motor running. Run time is directly proportional to the degrees of switch rotation.
Wilco
It's worth a lot to me.
It's 40* & wet today. I have to move the car onto the driveway to open the door far enough to lie on the concrete so I can get under the dash, so not much going to happen today.
I did find a picture of the rear of the panel:
[IMG]
[/IMG]
It's 40* & wet today. I have to move the car onto the driveway to open the door far enough to lie on the concrete so I can get under the dash, so not much going to happen today.
I did find a picture of the rear of the panel:
[IMG]
[/IMG]
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I dont think that is part of a C5.. Could be wrong. All my cars have been Dual Zone HVAC but, the actuator for the manual HVAC should not be much different than a dual zone except you only have one actuator and one temp door..
BC
BC
Burning Brakes
Joined: Mar 2011
Posts: 1,048
Likes: 5
From: Metairie LA
Just took mine out of the box and that's essentially it. HOWEVER the one pictured is BROKEN. The round thing on the left is a vacuum distribution valve of some sort. There is an assembly that attaches to the silver colored shaft, that has what I'll call a "vacuum distribution manifold" (for want of a better term) that has 6 vacuum nipples on it.
Last edited by PhilsFRC; Dec 29, 2012 at 03:12 PM.
Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 838
Likes: 0
From: Member since May 99 (Before 99 CF Crash & Burn) Georgia
I had forgotten that the battery was replaced (disconnected) in June when I returned for a couple of days.
Since the motor runs when the temp control is turned and the motor runs longer when the control is turned further, it seems that the control panel is functioning properly. (Which is actually too bad since replacing the controls would be the easiest repair.) But the car had not been cranked for two days when I listened, so any required vacuum-assist was probably not available
So IF the switch is good, what does that leave?
Since the motor runs when the temp control is turned and the motor runs longer when the control is turned further, it seems that the control panel is functioning properly. (Which is actually too bad since replacing the controls would be the easiest repair.) But the car had not been cranked for two days when I listened, so any required vacuum-assist was probably not available
So IF the switch is good, what does that leave?
- There are no codes. Does the Dual Zone always throw codes when it is bad?
- PhilsFRC pointed out that one of the control switches has a vacuum "octopus". That may be to the air output selector system.
But there appears to be two other vacuum connectors on the lower rear center of the panel where the temp switch is located. What is the easiest & fastest way to check vacuum in the HVAC switching system?
What else might be in play (or not working properly)? - ?