I have a 1995 STS.

Was driving it the other day, and the A/C just suddenly stopped working. It was after I turned the car off, in the middle of the day (about 95 degrees), and restarted it, since it hasn't worked.

The compressor is not engaging. When I push "auto," to turn on the A/C, the fan spools up to the max-cool speed, but the compressor doesn't engage. So I am thinking it is an electrical problem, but all the fuses work fine (tested them all including the relay).

I also check to see if there are any codes, which there aren't any (not bad for a '95 with 155k miles eh?).

After reading some other A/C posts on here, I still can't figure out where to start! What else could be the problem? Should I try to refill the refrigerant before I spend $2000 by taking it to the dealer?

Thanks for any help, Jim

First thing to do is get some A/C gauges and check the pressure's.
Harbor Freight has a set on sale for $39.

Post the results and we can guide you from there.

Check the electrical connector on the compressor and the relays if the pressures are OK. That said, if the pressures were low, you should have gotten a LOW REFRIGERANT message and a DTC.

I tested the pressure and it was OK. So I took it to the shop, and they said it was the "high-side" connector, and it wouldn't turn the compressor on. I am not sure exactly what they said, because I've never heard of it, but they want $200 to drain the system, replace the faulty part, and then recharge it. Worth it?

I don't know much about pricing, but that does not sound too bad, especially if you want A/C.

Also, is $600 a reasonable price to replace a water pump that had been leaking coolant?

I ask this because as I took it in for the A/C, I asked them to check to see if they could find the coolant leak, and they said it was the water pump.

No it's not. Shop around. Book time for that job is 2.2 hrs
The pump is under $100. Even at $100 an hr that's $300 tops.

"Book time?" I am probably naive here, but what book?

Dealers (Cadillac, etc) have a warranty time guide, independent shops have a labor guide.
Chilton, Mitchell and several others. I have a Chilton guide. And
2.2 hrs is generous. Most good technicians can change a Northstar pump
in less then an hour. Labor guides are what repair shops use to quote a job.
Times can vary a half hour one way or the other, that's why they're called guides.

An AC-Delco water pump part # 251-660 is $89 at Advance auto.
Check around, you can probably find a cheaper price somewhere.
That gives you an idea how much they are trying to make on you.

Not to mention that it is one of the easiest water pump in the world to change. Don't let them tell you otherwise.