I have a lennox compressor that won't stay on. It is 5 years old and has been fine until this week. It will run for a few minutes but won't stay on as it should. I initially thought there was a problem with the thermostat so I replaced it, but the problem persists. I did mess around with the contactor a little--if you push it in manually, the compressor will kick on. It just won't stay on. As soon as I release pressure on the contactor, the compressor shuts off. I know there is supposed to be 24 volts to the contactor to make the coil pull the contacts in, but I'm not sure which wires to check. There is a wire on either side which come in from the thermostat, but there is no voltage between them at all. I'm not sure which ones to check or what to do next. Can anyone steer me in the right direction from here? Thanks!