HVAC control module

GregP · June 19, 2001

Hi,

Got a quick questions on diagnosing a dead HVAC control module. Everything was working when I shut the truck off to drop my daughter at school, and the AC/vent functions were dead when I got back in a started it up again. The truck is a 1995 4WD 1500 Suburban with dual air.

The fan switch and rear defogger work, but all other functions (AC, air selector, temp control) up and died suddenly. I checked the fuses (all good), and pulled the dash open to confirm there is power to the control module at the AC relay, and at the AC on switch.

That is about the extent I could check, without knowing where else on the PC board I should be able to measure voltages or resistances.

Before I drop in a new ? module, does anyone know any other quick tests I could/should do? My electronics test equipment is limited to a digital meter.

Thanks - Greg

GregP · June 21, 2001

Just thought I'd give a wrap-up. It was the control module, as I replaced it last night and all now works. Tne new module is (of course) and improved design, bearing no resemblence on the IC board to the prior unit).

Apparently the unit had been dieing progressively for some time, as the AC is now significantly colder when on "full cold" setting. Guess the temp adjustment circuit had been going gradually to warmer independent of where the knob was set.

-Greg