Hi.

I just moved into a new apartment and am having issues with the AC unit (central air). The AC works fine until the compressor is turned off by the thermostat when the apartment reaches the proper temperature. However, after that, when it starts to heat up again and the AC kicks back on, the compressor fails to start. If i shut off the fan and then start cooling again, the compressor turns on. It seems that the compressor can turn on initially but when it is turned off during the cooling process it can no longer seem to turn back on without me physically going to the thermostat, turning cooling to off and then turning cooling back on. It's a Trane unit not sure what model, probably from 2008. Any ideas would be greatly appreciated. Have replaced the capacitor no change.

 

Welcome to the forums.


When the stat is satisfied the blower and the condensor both turn off unless you have the stat set to FAN ON mode.

What you're describing sounds like a stat problem but I'm not certain yet.

 

Thank you... interestingly, even when I just set fan to ON vs auto this problem occurs.

 

If you have a voltmeter/multimeter, check voltage between the R and Y terminals either at the thermostat or at the air handler. When the thermostat is calling for cooling, there should be 0VAC between the R & Y terminals. If the thermostat isn't working properly, you should measure ~24VAC between the R & Y terminals. If you don't have a volmeter, you could try temporarily jumpering the R & Y terminals to see if that makes the compressor start up.