'85 300SD No Tach No AC; OVP?

[zbynum]

Hey all, been struggling with this for a while. Lots of confusion between different model years and such; here is the info i know and have verified.

-1985 300SD does not have a tach amp, only a diagnostic port so my pins are not floating causing my tach to not work, they simply aren't there.


-My compressor clutch does not turn on and my AC does not blow cold. Been this way since i bought the car.


I know the OVP ties into this equation somewhere i just don't know how.


-My OVP blows its 10 amp fuse as soon as you plug the relay into the fusebox even when the car is off with the key out of the ignition. I took the OVP apart and re-soldered every pin on the board and it still blows the fuse when i plug it in.


My research:
Climate control needs a tach signal to turn the compressor on. OVP powers tach (maybe)


Im lost, help!