Ok here's my problem.
I've got a heat pump and the outdoor unit won't come one. I can make it come on by taken the panel off the outdoor unit and pushing in the contactor. After pushing and holding the contactor in, the compressor along with the fan will come on with no problem but goes off as soon as I let go. My mother-in-law lives next door with a unit exactly like the one I'm having a problem with. Her's works fine.
What I've done is taken all my parts out of my indoor unit and outdoor unit to her house and put them in her unit one part at a time trying to figure out which part isn't working. No luck. Every part when taken out of my indoor and outdoor units and put in her's worked.
I've even switch out my thermostat thinking that was the problem with no success either. The indoor unit blower comes on along with the emergency electrical elements. The problem is that the contactor on the outdoor unit isn't engaging sending 240V to the rest of the outdoor unit. So, I replaced the contactor thinking it was bad. Still nothing.
Keep in mind that I've tried all my parts one at a time in my mother-in-law's unit an each component worked. All that B.S. took probably 5 hours.