Ok, I have one last thing to fix on my Vette and it will be perfect. Since it's going to get colder soon I decided to try the heat last week and got nothing. So I read the forums and found out many people resolved this by flushing the heater core. I just finished flushing the cooling system, and the heater core. I filled her up, bleed out the air, and turned my auto climate control to 90. There was no heat, but then I realized the AC compressor was on full . I'm guessing the heat works just fine but the compressor isn't turning off so the air is neither hot or cold. Does the compressor always run? Does anyone else have this issue? Is it a problem with the auto climate control unit?

 

Well, after reading about the climate system on the forums. I have heat whenever I use the Face or Foot buttons. But no heat when I use Auto and Face/Foot buttons. I guess this was the way the car was made. I'm just glad I finally have heat.

 

The compressor should not be on if you are using the heater. it is either a seized compressor clutch, a sticking relay, or a problem with the controller. note that most cars will turn on the compressor if you select a defrost mode, even with the heater on. if you are not in a defrost mode and it keeps running, unplug the compressor. if it stops then the problem is in the relay or controller. if it keeps turning the compressor clutch is seized

 

Maybe I am having a problem with the relay, since I get no heat when in AUTO or bi-level. The forum link below made me think the compressor would come on for all modes except for the upper and lower settings:

http://forums.corvetteforum.com/c4-t...on-a-93-a.html

It would be nice to have heat on the AUTO and bi-level settings, I'll have to investigate this further.

 

I'm not familiar with how these cars are wired, but if there is an auto setting, that would indicate there is a thermometer of some sort that relays the cabin temp to the controller. if this sensor has failed it may be telling the controller its 300 degrees inside so its trying to cool the car until it reaches your selected auto temperature, which will never happen if the temp sensor is faulty. Look into that....

 

Thanks for the input, but I don't think it's the temperature sensor. When it reaches the desired temp set in auto mode for cooling, it will dial back the cold air output. That leaves me to believe the temp sensor is working.

 

The HVAC system will run the compressor when you go to defrost mode to help remove the moisture from the windshield.

The compressor shouldn't run when the inside temperature is lower than what you set on the controller.

The compressor is controlled by the controller mounted in the evaporator housing (on the firewall). Check the fuse by the blower motor. It's part of the feedback circuit from the blower/compressor controller to the HVAC control head.

 

Compressor is engaged in any Auto position temp with compressor engagement controlled by the Low Pressure Switch. The air temp is controlled by a door between the Evaporator and Heater Core with the interior temp thermistor or sender ignored at 60 or 90 - though that only keeps the blower humming at Max at those settings - it has nothing to do with whether or not the compressor is engaged. Start by seeing if the Temp Door is moving. Remove the Blower Module on the Evaporator Case and look inside the box while someone operates the Temp Controls from 60 to 90. If the door doesn't move, the motor that controls it is either broken, though usually it's the link holding it to the linkage. For the early years, it's a plastic piece; later years it's a gear (also plastic I think - someone around here actually found the gear from a vendor somewhere).

If the door is moving, then the only other reason would be a plugged up core. There's a check valve on the later years from the expansion tank to the core and it sometimes plugs up so check that out if it has one. If it's the core itself, coolant is flowing over the top but not through it. The only way to verify that is to remove it and run some hot water through it - if the sides aren't nice and toasty, it's plugged up. Otherwise, try some compressed air with your finger over one of the pipes. Fill it up with 15 to 20 psi and remove your finger to see if that will dislodge whatever is clogging it up.