not getting 240V to contactor on Carrier AC unit

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Old 05-31-14, 03:31 PM
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not getting 240V to contactor on Carrier AC unit

OK, I looked and searched a bit here and can't find my exact problem.

The issue started with no cooling, but the inside fan was running. I checked outside and the fan there was not running. It looked like a bad capacitor (bulged) so I replaced it.

Still it won't run. Here is what I've checked:

-good voltage (24-27) at the thermostat connections
-the in house unit seems OK (LED indicates getting 24V)
-basically no voltage (about zero volts) at the feed side of the connector
-when I turn the unit on, the contactor does activate and pulls the plunger in, but of course nothing happens since the 240V feed is not active

There is only one circuit breaker for this, on my main panel in my garage. There is no outside mounted breaker like many have.

So the low voltage control side of the equation seems to be working, but the high voltage supply is not. I can't see where this is being interrupted. We have a two zone system so I have one working unit to compare to.

I don't have $100/hr to have some repair man diagnose this, and I'm pretty darned handy if I have the knowledge of what is supposed to do what. That said, after a few hours reading posts and watching YouTube examples, I'm stumped.

Any help would be most appreciated.

Thanks.
 
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Old 05-31-14, 03:39 PM
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Well, if there is no outside disconnect, it's a straight shot from the dual/ganged (whatever the correct term is) breaker (can't be just one for 240V) to the contactor. You'll need to meter at the output side of the breaker (be CAREFUL!) and then at the contactor. If it's at the breakers, but not at the contactor, you have some sort of bad connection or a broken wire.
 
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Old 05-31-14, 03:46 PM
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There is probably another breaker just for the AC.
 
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Old 05-31-14, 06:10 PM
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There was another breaker - thanks for the motivation to keep searching for it.

Turns out they are not located near the AC units like the others I saw. Instead the breakers are in a box that is an extension of the box holding the power meter on the side of the house. Of course the one for the problematic AC unit was tripped, so I reset it an all seems OK now. The air from the receptacles seems cool, but tonight is very mild and we have the windows open, so I won't really be able to test the compressor function until tomorrow afternoon when it warms up again.

Thanks!

Atlas

PS Hey Gunguy45 - I'm a 45 guy myself. My phone number ends in 1911....
 
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