Alright so... If a contactor is not pulling in, I've found that most will go buy a new one, put it in and same thing, it won't pull in. Before going to get a new one, make sure there is power across the coil, for instance, if it's a 24v coil there should be 24v present with your meter leads set to volts and a lead on each side of the coil terminals. Here's where it gets tricky... Let's say you measure from ground to the coil inlet and get 24v, this means control voltage is present, but then you check across the coil and get 0v and the contactor is not pulling in. In most cases this means that the common is broken somewhere in the circuit. So here is my tip to test the contactor so you don't go buy a new one for no reason. Shut off the power and connect the common side of the coil to ground, turn on power and make a call so that contactor coil receives power, if the contactor is good it will pull in. At this point, you will need to find where the common has broken or separated. #teachme

Posted by HVAC Know It All at 2021-04-03 13:05:49 UTC