Nest - Heat Pump Reverse Valve

[Tpobaw95]

Nest Learning Thermostat

I have had this this thermostat for over a year now. After the rolling blackouts in Tennessee during December 2022, the thermostat would not send a signal to the heat pump valve to switch back to cool air. I am thinking when the power outages happened, it caused the thermostat to short out. However the thermostat did not display any errors. I  ended up having to replace the thermostat because the warranty has run out. Nest support said there was no correcting the thermostat and that it would have to be replaced. 

Anyone know a solution without replacing the thermostat? 

[Houptee]

Have to test with a multimeter at the outside unit set meter to AC volts not DC.

Test if you get 24-30v AC on the O wire to C wire outside when AC is on.

If no voltage then the possibly the Nest is not sending the power thru the O wire or the O wire is loose or broken at the furnace screw or outside bad connection.

Or the reversing valve coil is open and power is going to it but the solenoid coil is bad so it doesn't switch position. You can test the Ohms reading of the coil with the meter.

Or the coil is good and getting power but the internal valve is stuck and not changing position.

[aatienza]

Hey Tpobaw95,

Checking in — we hope you've got the answer you're looking for. Let us know if you have more questions in mind.
 

I appreciate the help, Houptee.

Thanks,

Archie

[Tpobaw95]

Someone on YouTube suggest replacing the Nest Wiring Base. Said that sometimes the O/B port can short out during a surge. I have purchased a new base and will post results once I have them. Thx! 

[aatienza]

Hey Tpobaw95,

Sounds like a plan!

Thanks,

Archie

[aatienza]

Hey there,

I just wanted to follow up to see if you still need our help. Please let us know as we would be happy to answer any questions you may have. 
 

Thanks,

Archie

[aatienza]

Hello there,

Just checking in to make sure that you've seen our responses. Please let me know if you have other questions or concerns as I will be locking this in 24 hours if I won't hear back from you again. Feel free to start a new thread and we'll be happy to help.
 

Thanks,
Archie