A/C not working...thought it was thermostat
#1
06-22-22, 04:44 AM
A/C not working...thought it was thermostat
Yesterday my central A/C unit fan was not turning and room temp air was coming out of the vents. Doing some troubleshooting, I checked the filter, reset the furnace and a/c circuit breakers. Nothing. I took the smart thermostat off the wall and wired the RGY wires together and it worked fine. I later put the thermostat back on the wall and it worked. I woke up today no A/C (furnace running, outside A/C fan not spinning). I took the thermostat off the wall and wired RGY again, still no cold air.
Anything else I can check before calling out an HVAC guy?
Anything else I can check before calling out an HVAC guy?
#2
06-22-22, 05:56 AM
Member
If you have a voltmeter, you could check to see if you have 24VAC across the low voltage (coil) terminals. If no voltage is present, check for voltage at the wire nuts where the low voltage cable attaches to the internal wiring of the outside unit. If you have 24VAC there, but not at the contactor, your system is probably low on refrigerant, resulting in the low pressure switch opening.
CAUTION: Before checking for 24VAC in the outside unit, disconnect the 240VAC power going to the outside unit. There should be a disconnect box near the outside unit. Since the 24VAC comes from the air handler/furnace, you don't need the 240VAC turned on, and it's safer working on the unit with it turned off.
CAUTION: Before checking for 24VAC in the outside unit, disconnect the 240VAC power going to the outside unit. There should be a disconnect box near the outside unit. Since the 24VAC comes from the air handler/furnace, you don't need the 240VAC turned on, and it's safer working on the unit with it turned off.
#3
06-22-22, 06:17 AM
Update: after reading a bunch of troubleshooting stuff, I turned the furnace back on and went outside and used a long screwdriver to give the fan a spin clockwise and it started to turn and the AC is working. Based on what I read, that means the capacitor is bad. Is that right? I was thinking to open it up and find out what capacitor I takes and get one and replace it. Is that the right course of action?
#4
06-22-22, 06:22 AM
Member
While not guaranteed, having to give the fan a spin is usually a sign that the capacitor is probably bad. For the few dollars that it costs, it's worth replacing to see if that solves the problem. If the fan spins easily, the motor is probably good. On the other hand, if it doesn't turn easily and smoothly, the motor bearings are probably bad and the motor should be replaced. Note that if you do have to replace the fan motor, the replacement may take a different value capacitor than the original motor.
It goes without saying that you MUST turn off the 240VAC power to the outside unit before attempting to replace the capacitor.
Good Luck!
It goes without saying that you MUST turn off the 240VAC power to the outside unit before attempting to replace the capacitor.
Good Luck!
#5
06-22-22, 03:06 PM
The last 3 times I tried to turn the a/c on (giving the fan a little push to get it going), the fan spun at normal speed but the air coming of the vents is not cold. I ordered a new capacitor. Is there anything else I can do to get the AC on in the meantime? Is this indicative of another problem?
#6
06-22-22, 05:00 PM
Member
The primary purpose of the condenser fan is to keep the compressor cool. If the fan isn't running, the compressor will overheat and the thermal cutoff will shut the system down. However, it appears that you have more problems than just the fan not wanting to start. Assuming it's a dual capacitor, one side is the fan capacitor, the other side is the compressor capacitor. If both sides were bad, it's possible that the compressor wouldn't start in addition to the fan not starting. However, if the compressor isn't running, it should be fairly obvious from the sound, or rather the lack of the compressor "buzzing".
If you expect to get the new capacitor soon, you may as well wait until you replace it and see what happens. However, there's a good chance that the capacitor won't solve your lack of cooling problem.
If you expect to get the new capacitor soon, you may as well wait until you replace it and see what happens. However, there's a good chance that the capacitor won't solve your lack of cooling problem.
PJmax
voted this post useful.
#7
06-22-22, 11:24 PM
Group Moderator
As mentioned..... replace the cap first.
If the compressor is going into thermal shutdown.... it can take a while to cool down.
Just restarting the fan spinning is not enough.
It needs to cool down before it will restart.
If the compressor is going into thermal shutdown.... it can take a while to cool down.
Just restarting the fan spinning is not enough.
It needs to cool down before it will restart.
