HVAC Control
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Joined: Aug 2011
Posts: 88
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From: DeWitt MI
HVAC Control
On my '89 Coupe I have standard Heat/AC. The controller is not operating properly in that the temp control will not move all the way to 'cold', and the selector switch seems to bleed forced air through all vents regardless of the setting.
When on "Normal" I get defrost as well as the center vents. When on "Heat" I also get bleed-air through the center vents.
I understand this is an electronic controller - not the old-style cable operated unit. Is this rebuildable, or must it be replaced? And - any ideas on where I can locate a new unit, or have this one re-worked?
Thanks!
When on "Normal" I get defrost as well as the center vents. When on "Heat" I also get bleed-air through the center vents.
I understand this is an electronic controller - not the old-style cable operated unit. Is this rebuildable, or must it be replaced? And - any ideas on where I can locate a new unit, or have this one re-worked?
Thanks!
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
There's still a Cable, but it only goes to the Heater Box to control temperature. The positions on the **** cover and uncover vacuum ports that suck open doors on the Heater Box to control where the air flows. Yours may be shot, or it could be a source problem which begins on the Intake Plenum - next to the Fuel Pressure Regulator Hose - travels behind or in front of the Distributor to a Check Valve near the Brake Booster that sends one side to the Vacuum Tank in the left Headlight well and another side back to the ECM harness on the right side. There it travels through the Firewall to the Controls in the Dash. Check the Checkvalve and the Source Connection first and/or, if Cruise isn't working, the Vacuum Tank. I don't know if anyone rebuilds the Controls.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
You said standard heat/AC and then you said electronic. There are two different HVAC options: C60 "manual" and C68 "automatic". The C68 is electronic, the C60 is not.
If your unit has a temperature display on the front panel then it is the C68 option.
If you have a lever that you move back and forth to control the temperature then it is the C60 option.
You said "temp control will not move all the way to cold", which implies the C60. In that case there is a cable from the temp lever to the heater core housing. It contols the position of the "blend door", which controls the temperature inside the car. You can get access to the blend door by removing the passenger side kick panel under the dash (a few 7mm screws).
As SunCr mentioned, the various air controls in the cabin are controlled by vacuum. The vacuum check valve frequently fails. It is a $4 part at any auto parts store. Yours is next to the distributor on the driver's side and will look very similar to this:
If your unit has a temperature display on the front panel then it is the C68 option.
If you have a lever that you move back and forth to control the temperature then it is the C60 option.
You said "temp control will not move all the way to cold", which implies the C60. In that case there is a cable from the temp lever to the heater core housing. It contols the position of the "blend door", which controls the temperature inside the car. You can get access to the blend door by removing the passenger side kick panel under the dash (a few 7mm screws).
As SunCr mentioned, the various air controls in the cabin are controlled by vacuum. The vacuum check valve frequently fails. It is a $4 part at any auto parts store. Yours is next to the distributor on the driver's side and will look very similar to this:
Last edited by Cliff Harris; Jul 23, 2013 at 02:19 AM.
Team Owner
Joined: Sep 2003
Posts: 25,385
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The "bleed" you mention is generally thought to be either a fault of the vacuum select switch in the control or the multi-ported vacuum harness that connects to it. Here is an eBay link to a control and using the "zoom" function you can see the several pieces of the C60 control. Sometimes eBay is a "great tool":
http://www.ebay.com/itm/1984-1989-C4-CORVETTE-MANUAL-AC-SWITCH-USED-GM-16040111-15-71414-/181147262533?pt=Motors_Car_Truck_Parts_Accessories&hash=item2a2d37de45&vxp=mtr
The vacuum switch GM 16040637 has not been available for quite some time. They do surface from time to time.
The electrical (brown) select rotary switch is also suspect to failure 16018267 is the part number for that and there's eBay availability and images available also.
http://www.ebay.com/itm/1984-1989-C4-CORVETTE-MANUAL-AC-SWITCH-USED-GM-16040111-15-71414-/181147262533?pt=Motors_Car_Truck_Parts_Accessories&hash=item2a2d37de45&vxp=mtr
The vacuum switch GM 16040637 has not been available for quite some time. They do surface from time to time.
The electrical (brown) select rotary switch is also suspect to failure 16018267 is the part number for that and there's eBay availability and images available also.
Last edited by WVZR-1; Jul 23, 2013 at 03:51 AM.
Intermediate
Joined: Jul 2013
Posts: 27
Likes: 0
How do I get access to the C68, my AC does not function, the c68 sometimes is on and sometimes off. I took off the panels and started to remove the panel that surrounds my shifter but can't get that panel out of the way. Seems to be stuck, so not sure what's holding it. Boot is a little stiff, what's trick folks?? Same time the radio (not stock) also does not function, no power. Just got my 87 and these are some of the last issues to conquer. Thanks for any help.
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Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The clock and AC both share the CTSY/CLK fuse. Sounds like yours is blown.
Intermediate
Joined: Jul 2013
Posts: 27
Likes: 0
Thanks so much. It's stuck in front actually. I'll look up what you mean by center bezel and interesting about the possible fuse, because the lights on the heater/AC unit are intermittently on and off, while the radio an after market one, has never powered up and it was a mess of wires behind with some not seemingly connected. I'll take some pictures of the loose wires and post them soon. (Hate when work gets in the way of fun)