Bought this 240 (1991) over the winter and the PO told me the a/c needed a little work, apparently it used to work and then just croaked on him. Got bored today and fooled around with it and here's what I've got so far:

There was power to the switch on the dash, but no power to the low pressure switch. I figured the relay was toast so I tried another one and sure enough, I got power to the low pressure switch. I could only get power to one side of the switch so I'm assuming the system is low or depleted of refrigerant. I jumped the switch to see if the compressor would kick on, and it did, but of course no cold air.

The car hasn't been retro fitted for r-134a so that's a must I'm assuming. One thing I noticed is that on the side of the car where the low pressure switch is, there are two ports for the a/c system that are under plastic caps. The smaller one just looks like a Schrader valve so I'm assuming it's the low side port. The other one is larger and I wasn't sure what it was, there is a bunch of green goop under the cap though. Maybe they pumped it full of dye or stop leak at some point?

Anyway I'd like to get it working again, just not sure what the next step would be in identifying what's keeping it from working properly. I'm assuming there's a leak somewhere since the system has very little pressure, also worried about the green goo from the mystery port.

What do you guys think? Worth messing with or is it just Pandora's box?