i have looked through a lot of threads but havent found the cure

1985 300dt a/c was working well until today. now the compressor doesnt kick in.
i jumped the wires on the evaporator and it still wont engage (i think this is a good thing) so i think the freon charge is good.
the tack is working and all the climate controls fan speeds and blower ports work fine.
i hope its the klima relay or fuse to the compressor however i dont know where to look/do first.

any ideas?

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http://i166.photobucket.com/albums/u116/OC03/240d.jpg
Current Car:
1985 300DT 55K miles