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1988 C4 when I got it the a/c was cold. One morning it was chilly so I turned the heat on. Now that's all I have is heat. The climate control keeps flashing between 60 and -88 and all the lights on the climate control flash on and off and now it just blows hot air. I've closed all the vents on the dash but even with the top down it gets hot inside. Any suggestions? Looking for a cheap solution for now as I can't afford taking it in for a new system. Help!!!
Thanks for the suggestions. I'd rather not bypass the heater core. Trying to avoid redoing rhe climate panel but I guess that's my only option? Is it possible some door got stuck in the wrong direction? Was hoping it would be that simple.
How do I access that? This is my first corvette so I'm learning as I go. I've already done a new battery and alternator, power steering pump and fuel pump. I got the one owner car for $4300. I think I did okay but as expected I'm having to repair tired parts. I'm gonna have to have the Atari dash done too. I can see speed and tach if I wear polorized glasses but barely can see fuel and temps (though it seems to run about 215 when hot in stop and go and about 185-190 in the cooler mornings).
Take the blower control module out of the HVAC ducting. This guy:
Look through the opening and you will see the temperature blend door. It determines what the temperature will be. Put the HVAC control panel at max cool (60° if you have the C68 HVAC system). The blend door should look like this (door covering heater core):
Then set the HVAC at max heat (90° for the C68 system). The blend door should block the opening into the center part of the duct, forcing all the air through the heater core:
You could put a ball valve in one of the heater hoses with barb fittings, very little coolant lost with this on in cool weather, off when hot out. Or fix correctly.
Last edited by A Peter C4; May 31, 2017 at 11:52 PM.
Thanks Cliff. I opened the access and the door was on the heat side and nothing I did from the inside changes its position. I used a long screwdriver and flipped it and now once again have ice cold air in the cabin. Now to figure out why it's not flipping but for now anyway I'm happy to have cold air blowing into the car rather than the hot air I've been suffering with for the last couple months.
Originally Posted by Cliff Harris
Take the blower control module out of the HVAC ducting. This guy:
Look through the opening and you will see the temperature blend door. It determines what the temperature will be. Put the HVAC control panel at max cool (60° if you have the C68 HVAC system). The blend door should look like this (door covering heater core):
Then set the HVAC at max heat (90° for the C68 system). The blend door should block the opening into the center part of the duct, forcing all the air through the heater core:
Just took it for a test ride and I heard the door flap and the hot air came back. Going to duct tape it closed for now until I can figure out what's causing it to do that. Any suggestions?
This is your AC / heater air blend door motor. This rod attaches to the door you saw looking down the blower control switch hole. Looks like your clip has broken.
I had a metal fastener made for $9. Found a nut that screws over the threads of the rod and had a 1" dia. bolt welded to it.
Where woukd i access tgat par of the door? How much dash to I need to remove to get there?
Originally Posted by HAD2HAV2
This is your AC / heater air blend door motor. This rod attaches to the door you saw looking down the blower control switch hole. Looks like your clip has broken.
I had a metal fastener made for $9. Found a nut that screws over the threads of the rod and had a 1" dia. bolt welded to it.
Remove the lower carpeted hush panel, which is a pain, and look up and you will see the motor, held on by 2-7mm screws, and also see if the rod is connected to the motor by that white plastic piece. You may have to remove the passenger seat to give you room to work.
The diameter of my bolt is not one inch but one-quarter inch. My bad.
So before I try and get at the blend door motor I tried to wedge the door open to the cool side. I did this and had cool air the whole ride and my climate control quit switching and blinking constantly and stayed on the 60 auto ac setting. Does the fact that the door was blocked give any new onsite into which part I need to replace? I'm thinking the blend door motor is working but just keeps switching between hot and cold and preferred to stay on hot but now with it forced cold my blinking climate control seems to have stopped blinking and is functioning as it should.
If the ac/heater door moves freely, then that white clip that attaches to the door motor is broken. But you should see a white clip on the door you are moving with your long screwdriver. If that one broke then your problem has become more difficult. Check and see if that clip is still on the rod that attaches to the air door.
You can get by this summer if you can wedge the door to the ac side. I used a sock. Don't push temperature buttons just the fan speed. Leave the temp settings on 60. At some point you will have to deal with this later.
I replaced the passenger side"bread box" long ago so when I fixed my broken clip I removed the top dash, the lower hush panel, a few plastic vent tubes, and the EMC so I could sit in the passenger seat and do all the work looking down. The bread box is held in by several 7mm screws and can be difficult to pull out.
The blend door is controlled by the HVAC programmer. The programmer is attached to a bracket bolted to the inside firewall above the gas pedal. It is held in place by one 7mm hex head screw.
Cliff, I am seeing the same AC/heater problems at least once a week on the Forum. Seems most of the time the programmer is not working and second is the plastic clip at the blend door motor is broken.
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Heater on
