I have an issue with my HVAC system. The A/C LED light on the climate control head unit just went out, blend doors are not responding to selector on the head unit, and the fan is not coming on, but the compressor is coming on even with the head unit set to all off position.


I unplugged the connector to the compressor coil to shut the a/c compressor off manually, and the fresh air and recirculate button LEDs came on.


I think my HVAC head unit is the problem, but is there anyway to test this or is it something else that could be the issue?


I have C68 fully automatic climate control and my truck is a 2000 Chevy Blazer LT 2WD and this all happened last night just as I am leaving work.

 

Although I have never taken the HVAC control assembly apart, I do not think there is much in the way of electronics there to go bad. But I have found that re-flowing the solder joints on everything has fixed the HVAC controller problem I had in a different Chevy.

Suggest taking the HVAC controller out, take it apart...carefully, re-flow every solder joint and try it.
Let us know what you find-out.

 

Update: The HVAC head unit is completly down (the only lights are the backlights come on when the headlights are switched on) and most of techs at my shop think it is the head unit itself.

They recommended I check fuses and connections before going further.

 

I have a RHD UK market Blazer with the Computer Climate Control. Mine failed in virtually the same way as yours seems to have done & the head unit was the culprit. It was several years ago but I remember having to unplug the connector at the compressor to stop it running all the time (the suction pipe was actually icing up all the time it got so cold). I bought a secondhand head unit & things have been fine since.
I maybe should have got the problem properly diagnosed before buying another unit but (to me at least) logic dictated that it had to be the control unit as nothing at all was responding on the panel. Of course I checked obvious things like fuses but they were all OK.

 

I got a replacement climate control computer a few days ago and everything does seem to be working again. I got a used control unit from eBay and I am just making sure it holds up for a least a month. From my understanding if the computer fails because of another electrical problem (outside of the computer itself), it will happen again within a month.