Testing Compressor Contactor?

[mkbug]

My home's AC unit stopped. I check the breakers and two fuses and have power to the unit. I took a volt meter to the black box and have power going in to this unit, but when its supposed to be on...there is no power coming out. Can I assume that is the correct test and this compressor contactor is bad?

We are in a heat wave this weekend in California - wife wants me to call a guy. But I think with The Garage Journal's help I got this...

 

[The Cobbler]

do you have power coming to the coil to activate it?

 

[bazar01]

See attached pic.
Use your meter to check if you have 24V on the terminals with green arrow.
If yes, you have 24VAC and still no 240VAC output, contactor is bad.

 

[bazar01]

Oops . Try again to attach pic

 

[nadogail]

A compressor contactor is no more complicated than any automotive relay, just bigger.

If you apply the appropriate voltage to the coil it should go "Clunk" if it doesn't something is amiss.

 

[mkbug]

I did some more testing...
I have voltage from the thermostat and into the circuit board. Photo 0797

But back to the contactor the black and blue wire had zero. Photo 0980

I followed the blue wire down to some connector on the copper line, and there was a button....I push it and heard a click. ahhhh Photo 0981.

But still nothing.

So I came back to my computer to do more research. Went back to the unit and viola it was working. Dont know why it all started again. But it is pushing cold air again.

What caused the button to pop? Do I still need a service call?

Thanks all.

 

[Wrench97]

Looks like the high pressure cut out switch, Is the condenser clean?
Fan on top running ok?

 

[nadogail]

You can now add HVAC Tech to your resume.

 

[brewchief]

The switch is a manual reset high pressure switch, dirty condenser coil or fan not operating is the normal reason that they will trip. Circuit board has a time delay that's why it didn't start right up.



Sent from my SM-T510 using Tapatalk

 

[mkbug]

Looks like the high pressure cut out switch, Is the condenser clean?
Fan on top running ok?

Fan was running but we did clean up some leaves etc. So much better now.


THANK YOU ALL THAT CONTRIBUTED.

Happy wife - happy life.

Martin

 

[Wrench97]

Wash the condenser out with a hose is usually all it takes.

 

[bazar01]

With your knowledge of how to use a volt meter , I knew you will be able to perform diagnostics.
Good job.

 

[rlitman]

A compressor contactor is no more complicated than any automotive relay, just bigger.

If you apply the appropriate voltage to the coil it should go "Clunk" if it doesn't something is amiss.

THAT contactor is no more smart than an automotive relay.
THIS one is quite a bit more smart, with short-cycle and brownout protection.

 

[LS6 Tommy]

I'd still give your coil a good rinsing. Some leaves should cause the HPCO to trip.

Tommy