Thanks for the suggestions chaps. I'll have a full on go at it this weekend. I have the merc manual, but reading that thing confused me, so I thought I would ask in case it is a common problem and there is an obvious fix. But looks like I'll have to do some sleuthing...

Larry,
The compressor doesn't turn on no matter what - defroster on, full a/c, whatever.

I don't know the system on the 124 so I guess I'll just have to mess with it. I don't know where the resistors are you talk about. But I think I will manually test the fuses with a DVT rahter than just a visual inspection.

BTW, what resistor and fan are you talking about?