I'm hoping that someone out there may be willing to help me by looking up a wiring diagram for the climate control system in a 1984 300D. I'm trying to determine which part is defective. Unfortunately, the service CD contains a very poor scan of the wiring diagrams, and it is all but useless for tracing the individual wires. As I quote the "item numbers" from the wiring diagram, I am looking at the 1983 schematic, since that is the one that is contained in the CD

I am trying to determine what supplies voltage to trigger the air conditioning compressor relay (item # 28 in the diagram, located in the engine compartment -- the one which engages the electromagnetic clutch on the AC compressor). Is the voltage for the relay supplied from the push button control unit (item No. 4 in the wiring diagram) or from the "electronic switching unit for temperature control" (item No. 9 in the wiring diagram)?

To clarify, I am not looking for the source of voltage for the compressor clutch itself, (which is supplied via a fuse) I am seeking the source of voltage that triggers the coil in the relay (terminals 85/86).

Thank you in advance for your help – it is greatly appreciated!

RTH