OT - Troubleshooting air compressor contactor

See attached picture. Came in this morning and found no shop air. Here's what I've tested so far:

-Proper voltage is supplied. Breaker is not tripped, no loose wires, etc.
-At the contactor, I am getting continuity between L2 and the back red wire as well as L1 and the back blue wire. I'm no expert, but I'm pretty sure those back two terminals are the ones that when powdered activate the contactor?
-As far as I can see, there are 3 safety switches. The pressure regulator, the thermal overload, and something that goes back to what looks like an oil filter? They are all wired into the back red and blue wires at some point and all 3 of which are showing continuity across the terminals.
-When I press in the center of the contactor, the compressor starts, but stops once I release the button.

So as far as I can tell, everything seems to be working properly, maybe just a bad contactor? It was replaced less than 2 years ago when I did a voltage change on the compressor (from 480 to 240). I just don't want to order a replacement if I'm not guaranteed that's the issue. Thoughts?

The back red and back blue wire are the one that should close the contactor. Continuity is interesting but not definitive, what is the voltage between those 2 wires? If you are maintaining you own stuff you need a multimeter.

Someone on ebay has that part number contactor listed for $16.99
New Eaton Cutler Hammer C25DNY13 3 Amp 28 24V Coil Contactor C25DNY13B | eBay

CarlBoyd

Don't know what you have for a compressor but many larger commercial units will have a low oil level switch that will kill the mag. Maybe the wires you can't ID go to the float switch in the crankcase. The control for the compressor is actually a momentary setup with the pressure switch closing and opening the circuit concurrent with air pressure. If your thermal over load is properly reset and the pump is full of oil (low oil switch) then the only other culprit, other than a bad mag coil would be a bum pressure switch.

Some pressure switches have a manual toggle lever on the side that you can flip to start the pump. If yours does..and you flip it and the thing starts then the coil is OK and the pressure switch is bum. Make sense?

Stuart

CarlBoyd said:

The back red and back blue wire are the one that should close the contactor. Continuity is interesting but not definitive, what is the voltage between those 2 wires? If you are maintaining you own stuff you need a multimeter.

Someone on ebay has that part number contactor listed for $16.99
New Eaton Cutler Hammer C25DNY13 3 Amp 28 24V Coil Contactor C25DNY13B | eBay

CarlBoyd

Click to expand...

Just checked, I got 238 volts across the red and blue terminal. I'm going to go ahead and assume that means the contactor is dead and needs replacing. Thanks for the link! I'll order it now.