One sign that a compressor is about to have problems is the rise in amperage it needs to start and keep running. Our old one was drawing 30 amps on startup and a continuous 18 amps while running ... normal units should be around 4 or 6 amps when running.Thanks, that helps me a lot. I like to know what might go wrong. Funny thing, I don't mind paying as much when I know in advance what likely will fail.
I asked when I last had the contractor over, how much would it be to fix one of my units. He said if it was the compressor, $1400 plus labor. I'm thinking that other problems are mostly just the labor, inexpensive capacitors etc.. Motors would be more.
When we initially bought our current house that we now live in we had to have major repairs done to the A/C - Gas furnace equipment. The previous owners seldom, if ever, changed the air filter on the A/C - Furnace intake. They had also installed the unit that sits on top of the furnace upside down because it was the only way it would fit ... and they had to cut it all apart to do that so all corners had duct tape on them ... and the flue to the roof was also not connected. It's a wonder the whole house didn't catch on fire during their occupancy.
We spent about $2,750 on those repairs and a few years later had to replace the outside condenser unit ... We opted to upgrade to the [then] latest "sear" rating and had a 5 ton unit installed. When our company comes to inspect they check out the refrigerant level and the total operation of the condenser, evaporator and even the furnace so that it will be ready for use during the winter.