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AC unit won't stay running

13221 Views 4 Replies 4 Participants Last post by  Doc Holliday
Hello all, I have a Bryant AC Unit Model #597CN042-A that is around 15 years old. Just this year, I have had issues with it not staying running. What happens is that, after 10 minutes or so of continuous running, the outside unit turns off, both the fan and compressor. After delving a little more into the electronics side of it, I found that the contactor drops out, but pushing it back in causes the unit to start back up. Thinking that it might be an issue, I replaced the contactor with a brand new one, however the same problem persists. When the AC unit stopped running, I checked to see if the main lines coming into the AC unit have the correct voltage drop across them, and they do (220 - 230 VAC). Then, I checked to see if there was any voltage drop across the coil of the contactor, and there was not (should see 24 VAC). I then checked to see if the call for cooling was coming in from the lines leading to the thermostat, and there was 24 VAC across those lines. With this in mind, I believe that it may be a few other things, but am not sure. I am leaning towards either the fan overheating, too little R22 in the system, or the high pressure cutoff switch on the compressor itself. Based on what I found out so far, I don't believe it to be the main capacitor as the unit does start up initially. I should point out also that if I let the AC unit sit for a period of time it will start back up, but then shut down about 10 minutes later. I am trying to resolve the problem myself so as not to shell out a fortune to a qualified HVAC technician, but in worse case scenario then I'll do what I have to do then. Any suggestions as to what I should try next would be greatly appreciated. Thank you.
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the fan and compressor come off the same contactor...first off.the cap has to be good either or couldn't run if it was shot.sounds like HI or LO pressure safty.restart the unit and grab the liquid line if it is super hot the condenser is dirty and blocked up.if it is LO pressure lack of Freon then the leak crap kicks in...had it had a refill every year or top off in past years...try that LL feel test first.whatever a good hosing from inside out with some light acid applied on a dry coil couldn't hurt...get back with what's up...
 

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the fan and compressor come off the same contactor...first off.the cap has to be good either or couldn't run if it was shot.sounds like HI or LO pressure safty.restart the unit and grab the liquid line if it is super hot the condenser is dirty and blocked up.if it is LO pressure lack of Freon then the leak crap kicks in...had it had a refill every year or top off in past years...try that LL feel test first.whatever a good hosing from inside out with some light acid applied on a dry coil couldn't hurt...get back with what's up...
I'll give the feel test a try. Another forum suggested it is most likely a safety switch somewhere, but the more I can find out myself first the better.
 
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