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The A/C external units (both fan and compressor) do not start sometimes. When I turn on A/C for cold air, then the only main unit starts and blows warm air.

The only way that works is that I turn off the entire A/C, turn off the breaker, and then start everything again. Then, the external units start and it blows cold air. I have to do this like every two months. What would be the potential issues?

  • The model number would be very helpful. If you are running it now I'd guess it's S.E.E.R. rating is at least 20. Higher rated air-conditioners have some internal controls that could be acting up. They also have on board diagnostics. If it's like 13-16 S.E.E.R. it would probably just be the fan motors start winding and the motor would need replacement. – Joe Fala Feb 24 at 20:24
  • Chattering contactors...failing start or start/run capacitor. Does it buzz or humm at the outdoor unit when it fails to start? – Jeff Cates Feb 24 at 20:31
  • @JeffCates Cates No it is just calm. When it started I found that it now stops after running about five minutes. – Chang Feb 25 at 0:04
  • If you feel confident in DIY, turn off the power to the outdoor unit AND indoor unit. Check the capacitor and see if it has a bulge. Like this: i177.photobucket.com/albums/w208/johnmeyer/… The bulge could be on the top as seen or on the bottom. If it is bulging, it is bad and needs replaced. If it is flat, then it should be good. Also, while you are in there, you could do a contactor test. Easy thing is to turn the indoor unit on, thermostat call for cool, and see/hear if the contactor is closing. – Jeff Cates Feb 25 at 5:45

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