So my thermostat is fried. Had a very capable HVAC technician take a look at it and he found this out. I have ordered a new one but it isn't going to be here for the next 2-3 days. I live in Texas and can't imagine being without AC for that long. So the HVAC technician "bypassed" the thermostat and turned on the HVAC. This means the only (two) ways currently to turn the HVAC on/off is either using the circuit breaker or using the compressor service switch.

I could keep the HVAC on always but my compressor has never worked this hard before (i.e. staying on all the time) and it is getting along in age and the last thing I want is a compressor failure. So my intention is to turn the A/C on/off by using the circuit breaker. I estimate doing about 10-12 on/off cycles before the new thermostat is installed.

My question is: is it OK for me to do this power up/down cycling for the duration I have indicated? Would that be worse on the compressor? Also, I recently had my TxV valve/evap coil replaced and do not want to damage those either. But I also cannot bear to be completely without A/C.

Any suggestions are appreciated.

  • 1
    Actualy you can still use the thermosta wires to controll the AC.
    – Traveler
    Commented Aug 12, 2022 at 20:41
  • 2
    Couldn't you just go to a big box store and buy a cheap temporary thermostat? Perhaps you could open it very carefully so as to preserve the packaging in pristine condition, then when done repack it in the original package. What to do with it after that I'll leave as an exercise for the reader. ;)
    – Glen Yates
    Commented Aug 12, 2022 at 21:06
  • 2
    Are you kidding me? Basic thermostats are like $20 and easy to swap. Commented Aug 13, 2022 at 0:16

1 Answer 1


Actually you can still use the thermostat wires to control the AC.

All thermostat does is to send 24 volt on the right wire to activate the AC or the fan.

In most cases the Y connection is used to turn on/off the AC.

The R (red) is the 24 volt on the thermostat.

Just connect the Y and the R on the thermostat wiring and AC and the Fan should run. If Fan does not run for some reason, then also connect the Fan output on the thermostat to 24 V.

Then disconnect when you had enough and repeat.

Since that is what your thermostat normally does anyway, not harm to the AC will be done, just give it some time between on/off.

It is only 24 Volt, so yes you can touch it with bare fingers.

  • 2
    I was thinking the same thing, the other reason to use the tstat wires is usually there is some sort of "ramp down" of the air handler after the compressor stops . Commented Aug 12, 2022 at 21:03
  • @GeorgeAnderson correct, the fan keeps circulating the air after compressor was turned off.
    – Traveler
    Commented Aug 12, 2022 at 21:18
  • If not comfortable touching bare wires, any cheap on/off switch listed for over 24 volts will work also.
    – crip659
    Commented Aug 12, 2022 at 22:01
  • All your instructions will do is create a block of ice inside the air handler. You forgot to call for fan. Commented Aug 13, 2022 at 0:14
  • @Harper-ReinstateMonica Actually you are wrong here. The Fan goes on in parallel to AC, always. That is how it is build (wired). AC newer runs without fan. But fan runs without AC in Fan only mode.
    – Traveler
    Commented Aug 13, 2022 at 0:35

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