The wires to the alternator were checked, at least that's what my shop claims. I'm thinking it might be the ac compressor clutch - I think the wires coming into it have bad insulation and may be causing a short. No other electrical device in the car causes any problem right now.
Is there any way I can change the wiring to the compressor without taking it out of the car (evacuating the AC system) ?
What's the normal amperage that should go into the compressor? I could connect an ammeter in series and check the readings, but I currently have a simple multimeter only capable of measuring up to 10 amps, and I'm afraid it might not be enough and I'd just blow the fuse in it.
I measured the resistance of the compressor's coil and it's 4.2 ohm, while it should be 3.6 +/- 0.2...

any ideas?