Yesterday our mid 1991 vintage Rheem AC quit working. I found the 60A breaker had tripped. I tried resetting it but it kept tripping. I pulled the slow blow fuses by the compressor and the 60A breaker set ok. Today I did some metering around the contactor. All wiring to the contactor was metered to be OK with input feed wires removed from contactor. I then reconnected the feed lines, removed the output lines going to the compressor, installed the slow blow and closed the 60A breaker. Everything was OK but the condensor fan turned on at half speed, which surprised me. I measured 145V across the output lines of the contactor, which I thought was an odd voltage. I then had my wife turn the thermostat to COOL and the contactor closed, the condenser fan ran a full speed and I measured 245V across the output of the contactor and 120 across each side to gnd. When she turned the thermostat off, the voltage dropped to 145V and the fan dropped to 1/2 speed. The power lines to the compressor were disconnected at the time so I'm not sure why the condensor fan was running 1/2 speed with no thermostat calling for cooling. With a single pole contactor is that what I should see with the compressor power lines removed with thermostat OFF?
Another thing that I found that I don't understand was with everything connected and the thermostat OFF, the 60A breaker trips right away. If the contactor is open (actually 1/2 open) should that happen normally or is it a sign of a faulty contactor?
I measured 6 ohms across the compressor HV feed lines with them disconnected from the contactor posts. Is that about right?
From what I can tell it's either the contactor is bad or the compressor is stalled, causing the breaker to trip immediately.
I would appreciate any comments, advice, or other things to do or check! I'm trying to determine who to call... AC service or new AC install. If that is considered DIY, then I withdraw my questions.