Heater / A/c / Vent Controller Inoperative

[EmTwo]

Hey Folks,

 

I have a 1990 C1500 Silverado; 5.7L V-8, Auto, all the trimmings.

 

I can no longer turn on Heater, A/C or vent; the controller backlighting is working, but the screen does not come up.

 

Thinking I had a bad controller, I found a controller on eBay, and purchased it, but no joy.

 

Of course, I've checked the Heater fuze, but it's good.

 

Checked my Chiltons and Haynes manual, but can't find anything to point me in the right direction.

 

Any ideas?

[EmTwo]

Disregard; while fumbling around putting everything back together, I moved a wire bundle that came out of the back of the controller, and the heater kicked in...I followed the bundle, and found it went to a series of relays behind the glove box.

 

I removed the glove box, and when moving the bundles around, found that the bundle going into one of the relays apparently has a loose pin.

 

Heater is now working, but will be removing the connector from the relay and resetting all the pins.