a/c dead on 560sl

[sms]

Hi,

My a/c has been not working for awhile. R12 has all leaked out. Gages read 0 for high and low side. Believe it is the compressor since there is a dirty oil residue on it, but the dirt could just be normal road dirt. Anyway, I partially charged it with a substitute refrigerant (just for finding the leak) that contained a flourescant dye. I got the pressure up to 60 on the low and 50 on the high side, but could not get the compressor to kick-in even when I shorted out the pressure switch. Refrigerant leaked out in 1 day and was unable to see the dye anywhere with a black light.

Why couldn't I get the compressor to kick-in and could the leak be in another component other than the compressor? How should I proceed?

Thanks!