Central AC not working walk through

[MikeB52]

Had a weird issue where the AC just stopped working.
Figured I’d share the steps for those, like me, that hate paying others to be observant where I can be.

So, furnace blower is running but ac unit outside is not.
Right there you can rule out condensate overflow or bad signal coil in the furnace.
Power down everything an hr, to allow a reset and thaw, just in case.
Check main house breakers for anything popped and reset.

Power up furnace and select cool on thermostat.
No change. Inside blower comes on, outside nothing.
Rules out frozen evaporator

Pull thermostat off wall and remove the red, yellow and green wires. Connect all three together.
No change, inner furnace on, AC unit off.
This rules out the thermostat. Put it back on and turn everything back on to demand.

Now you need a meter. Go out and verify you’ve got 240 vac at your ac unit disconnect across the poles, and 120 vac from each leg to ground.

pull out disconnect and move inside ac unit.
Check capacitor capacitance is as per nameplate. If so it ain’t that.
Check wiring at contact for broken bent wires.

Now power on disconnect and carefully test for 240 at input to contactor.
Coil should pull in when unit calls for cool, so you should have 24 vac across the middle of the contactor.



In my case everything to this point checked out, but ac unit did not start.
I didn’t have 240 on the top poles of my contact even though the unit did pull in.
Tear the contactor apart, voiding warranty!! Oh no!!

Dead bug there, but that’s not to bad, dig in deeper.

That’s some arcing burn evidence and the residue of something.

Earwig bbq anyone.
Lil shit walked through the contact at the wrong moment and got smashed inside. Then became an insulator across the pole.
Cleaned it up with sandpaper, and put everything back together.

System fired right up..
Just a lil share..
Cheers men.
Hope it helps one of you out