AC and Hearter control problem

I have a 91 Silverado k1500. It has the push button AC and heater control panel. The panel does not function - no fan - no heat - no air - no lights in the panel. The part number label is no longer on the panel but it is the style with the "RECIR" button rather than the "MAX" button (part # 16204785).


I installed a used 16204785 and found the same results. No function - no lights in the panel. I am told the replacement panel was tested aand worked.

There is current showing at some of the connector points on the truck side connector plug.

I have cleaned the connector points on the back of the panel and in the plug connection.

I have checked the fusable links near the fire wall and all seem fine.

I have checked the fuses under the dash and all are fine.

There are three relays behind the glove box. I think one or more have something to do with the AC. I have heard buzzing from these relays in the past but this has gone away. The panel did not work at all before or after the buzzing problem.

Any suggestions?

Thank you
JBB