scooby99

Tried using my heater a couple of weeks ago and all I get is cold air. Coolant level is good, both heater core hoses are warm, outside temperature sensor is reading correctly. What else should I check?

MORE INFO: I am getting heat out of the passenger side vents, but nothing on the driver's side. Do I disconnect the battery to reset the HVAC controller?

Thanks,

Sam

Kreeess

make sure ur temp is set to the highest temp? lol ive been guilty of thinking my AC doesnt work when i left the temp on high ! haha but on a serious note .. someone with more knowledge will chime in.. GL

Cutlassmaster

Pull the codes, write them down and then clear them. If mine acts a little weird as in not hot or cold enough, I clear all the codes and it resets it. Mine is a 99 and my buddies 97 and they both reset or recalibrate after clearing the codes. Sometimes it takes 2 - 3 tries but always seems to work.
GL
Chris

Kreeess

this

scooby99

I have not tried that. Will give it a shot tonight.

Thanks,

Sam

Cutlassmaster

When I do it I ensure HVAC and radio are off. Let is know if it works.
Chris

bobeast

Another thought... The damper doors which direct airflow to the various vents are controlled by vacuum which comes off the back of the intake manifold.

A common problem is battery acid leakage which eats into the wiring bundle that contains that vacuum line. It happened to me although I discovered it when attempting to control cold air from the AC.

mcgilles

This is almost certainly an HVAC actuator failure. More common on older C5s before a software update on the HVAC panel helepd some. The problem is either the door that blends the outside/conditioned air has warped to the point that the actuator's feedback signal goes out of range, or the actuator itself may have a cracked plastic gear inside. When the HVAC senses the actuator out of range it goes into a failure mode, which at least in the winter dumps cold air inside the car Pull the fuse on the HVAC and leave it out for 15 minutes or so. When you reinstall you'll hear the actuators index. See if the heat starts working again. When mine did this the fuse pull gave me about 30 minutes of heat before it would fail again. There should be a code set when this happens.<br />
To fix it you may get lucky and all you have to do is move the potentiometer gear a tooth or two (which diretion depends on side, there are posts on this I don't recall which way off hand) this basically compensates for the changed geometry of the blend door. That's all I needed to do and its been working great for a couple of years now. If the gear is broken I undestand it can be epoxied, or the actuator needs to be replaced. I think they are around $100 but its been a long time.<br />
<br />
getting to it is not fun. The driver's side it is possible but very difficult to reach from under the dash. The passenger's side you must take the dash pad out. Removing the dash sounds bad, but its actually not nearly as tough of a job once you've done it. If I had to do the driver's side one, I'd probably take the dash out for that one also (the shop manual method) from what I've read aI actually think that would be easier than trying to reach up there from underneith. Good luck!

scooby99

I have heat ... on the driver's side now. The passenger side, not so much. The defrost is now working, so I will probably leave it be for a while.

Thanks for all the suggestions. Now I just need to get rid of the ABS and TCS lights!

Sam

Cutlassmaster

As everyone else has said, it could be a couple if things but the easiest and quickest is to clear codes. Glad you have some heat now.
GL
Chris

pewter99

sometimes simply disconnecting the battery will allow them to reset if clearing codes doesn't work....

Cutlassmaster

That's how I figured out clearing codes worked if it was an electric issue. Disconnected buddies 97 after O2 sensors and he lost temp control on drivers side. Did battery again and no change. Ran codes and heard it cycling the servo and then it worked. Very strange but worked on mine when AC seemed colder on pass side. Could be multiple different things so try easiest ones first.
Chris