740 A/C Electrical Issue/wiring diagrams

[stephenpar]

Hello, all:
I did a search to see if there was any threads that would address my question and although several came close, none did.
I have a 1992 740 Wagon with Rex/Regina ignition and injection. The A/C clutch will not engage even though it has a good 134A charge. I tried jumping across the pressure switch on the receiver-drier and the three on the condenser but no joy. I also tried another used heater control panel ( I have the manual control head with a 5-position rotary fan switch on the left, a four position air flow direction rotary switch in the middle and a rotary temp control with declining red bars on the right, a recirculate air button on the left bottom and an "A/C Off" button on bottom right) and that did not make any difference but I have no way of knowing if the used one I bought was good or not. I have a Chilton manual and a Haynes manual, although the Haynes only covers up through 1990 or so. I would really like a look at decent wiring diagram. Do you know where I could find such? Do you have any idea where I might look next for the fault? The clutch engages if hot wired, by the way, and there is a hot red/green wire going into the back of the control head, but nothing seems to come back out of the head. Also, none of the panel lights work in either of the control panels I have.
Any suggestions? Anyone have a good wiring schematic for 1992 740 A/C?
Thank you,
Stephen
Columbus, Ohio
USA

[telmo]

I guess there is a temperature switch on the evaporator behind the dash...