My sister has a 2002 Nissan Sentra GXE and the AC hasn’t been working for almost 3 years now. She took it to a mechanic who told her it would cost over 1k to fix because the problem was that “the ECM switch was not grounding to the AC relay”. Admittedly I know very little about cars, especially the electronics of them, but I don’t trust these guys. This same garage told me that I needed to replace my power steering harness thingy (that’s how much I know about cars) because it was leaking. They verbally quoted me $700.00 for the work, which I declined, but when I reviewed the write-up they did on the problem later, the fine print at the end actually said the cost would be $1,100.00. Not only that, but I took my car somewhere else and they couldn’t find anything wrong with my power steering system. Long story short, I’m not convinced that the ECM switch is the real culprit of the Nissan’s AC problems.

Is there a way to test this ourselves and avoid another garage fee?

Not sure if this is related, but the speakers went out shortly after the AC pooped.

Any ideas/tips would be very much appreciated.