Air Conditioning - contactor contacts not engaging

My central A/C seemed to be working then the outside fan continued running after thermostat shut off downstairs unit. I went downstairs and found the small copper tube cold and the sound of the downstairs unit was like it was still running but it had already shut off at the thermostat. Not sure what that sound was.

I went outside and pulled the breaker and the fan stopped. I checked and found the contactor was worn. After I found the bad contactor, the outside fan was intermittently shutting off correctly before the contactor was replaced but sometimes I would have to go out and pull the breaker to shut off the fan.

Today I replaced the contactor and the coil at the outside unit along with some terminals that were loose or broken. I’m sure all the connections are good now and correctly installed, however I did not check any thermostat wiring.

When I start the A/C at the thermostat, it won’t start up till I go outside and hold the contactor contacts together. After that everything kicks on, seems to run ok. Why doesn’t the contactor kick in from the thermostat? Could there have been some damage to the evaporator coil when the outside fan continued running before the contactor was replaced?
Need some help, thanks,

What is the voltage going to the contactor magnetic coil when the thermostat is calling for cooling?

What is the voltage going to the contactor magnetic coil when the thermostat is calling for cooling?


What is the best way to check that voltage? I have a VOM but not sure which points of contact to measure the volts at.

look closely at the contactor, you should see the magnetic coil, test the 2 terminals that go to the coil.

The small wires..not the big ones...lol