1996 gmc sierra C2500 Fan speed issue

[prowles123]

Hello everyone I am having an issue i need some input on....
I have a 1996 gmc sierra c2500 5.7L
My fan does not work on the high speed and the ac commpressor doesn't engage when i press the ac button on the climate control any suggestions? I checked all the fuses and they are good and all other fan speeds work and all the ac light turns on when i press the ac button, i turn the fan switch to high and the fan stops working and i hear what i assume is a relay click by the glove box somewhere...

 

[WarWagon]

Control heads on these are not that reliable. Neither is the power to the HVAC 2 wire connector behind the glove box.
http://www.thetruckstop.us/forum/th...ers-w-blower-off-erratic-or-no-airflow.28385/

Assuming the above isn't the issue check the high speed fan relay for 12v and 12v coming out of it when you are in the high speed switch setting.

No AC with the light on is likely a bad low side switch or you are out of freon and the switch tripped due to that. Check for 12v at the switch and do a resistance test to see if the switch is closed. Open is likely low on freon. Wire loose on clutch, bad coil, or bad ground are also possible.