AC compressor not shutting off

[Kerry D]

I have a Carrier central AC system in my home and have an issue with it. The AC compressor is not shutting off, just keeps running until I flip the circut breaker. The air handler fan seems to be working like it is supposed to. I can turn the fan off and on by using the thermostat switch. I took the cover plate off of the compressor housing and checked the switches to see if the contactor was free and to look for burning wires and such. Don't see anything out of place. suggestions? thanks for your help !

[TURTLE]

This is Turtle.

Replace the electric cover and Slap the cover with your fist. It will knock the contactor loose. It sounds like you have a set of contactors that are sticking shut. Then call a hvac service company to come service it and have the contactor changed out. It can be bugs , ants, or any type critter getting into the contactors to do this. After you repair the unit. Put you some ant poison out around the condenser for better that half the time it is fire ants that are in the contactors.

Now I can't see it from here but this just sounds like what it is.

TURTLE

[Patch]

[Dan O.]

The switching on and off of power for the condenser (outside unit) is done *inside the house* not inside the condenser itself so looking there for such a problem will likely be futile.

As Turtle suggested you may have a sticking contactor (relay type thing) which is activated by the thermostat. Follow the thermostat's wires and you'll likely come to it. It will be where the full 240 supply them continues onto the condenser.

You can see illustration of a couple of A/C contactors at the following link:

Dan O.

- Appliance411.com

=Ð~~~~~~

[Travis Jordan]

Dan O. wrote: /snip/

/snip/

Sorry Dan, that's wrong. In virtually every residential 1-phase unit I have seen, the contactor relay IS inside the condenser housing. As Turtle says, look for a stuck relay due either to corroded contacts or even ants in the moving parts.

[jriegle]

In my unit, a 24 volt control line runs to the condensor unit to the contactor. All the condensor units I have seen are like this. My contactor was sticking closed. I spent $17 on a new one and so far so good. John

[*CBHVAC*]

Actually, correct. The thermostat is nothing but an off and on switch..however...99% of the time when you have a problem like this one, the problem is the contactor...outside...in the unit.

Ummm...thats IN the condensor...

[Kerry D]

I took the side cover off the compressor and found the contactor. Took the little screws out and looked at the points, bumped things around a bit and put back together. Everything works great now! I have had the bug problem with my deep well pump before so I guess this was much the same. Thanks for all the help!

[EL]

Actually I can see two downsides to having the contactor inside.

First, an electrical run from panel to contactor location to compressor is likely to be longer than just going directly panel to compressor. Longer run = greater I2R losses and/or a requirement for heavier wire.

Second is safety. Granted this would be a dumb thing to do, but it's not hard to imagine someone opening up the condensing unit, being "careful" and using a multimeter to verify there's no voltage there, then proceeding to do work and getting electrocuted when the remotely-located contactor decides to turn the juice on. I'd feel safer knowing that when I can't measure voltage inside the unit that it's really "off".

Eric Law

[TURTLE]

This is Turtle.

Once you ever have the contactor stick for some reason or the other. You will see the problem come back about 99% of the time in the next 6 months. Pay now or pay later.

TURTLE