Nest thermostat is on the fritz

[Jbergener]

I have had my Nest for over 3 years now.  It had been working great.  A couple months back it stopped running heat when it was supposed to be heating.  I did a factory reset on it and it started working again after that.

Fast forward to today, it got warm outside so we tried turning on the air conditioning.  It continued to blow warm air.  I did another reset on it and now it’s running the furnace and the air conditioning at the same time.

I have the HVAC system turned off for now and the Nest completely unplugged.  I’m debating whether I should try getting this thing working or just replace it.

Unfortunately tech support was no help.  They just kept telling me I need a C wire even though it has worked fine without one since day one.

Suggestions?

[Patrick_Caezza]

@Jbergener 

The Learning Thermostat 3rd gen will work for several years without a C wire and then it will start having problems which is caused by the missing C wire.

Follow the steps in this link and post what your thermostat power levels are.

Nest thermostat information menu 

[Jbergener]

Here is what it reads:

Battery

3.738 V

Voc

36.28 V

Vin

34.47 V

lin

40 mA (i)

[Jbergener]

After plugging it all back together it’s just running the heat non-stop and won’t turn it off.  I have to turn off the furnace at the breaker.

[Jbergener · Accepted solution]

I have removed my Nest thermostat.  Too many issues.  I’ve replaced it with a dumb thermostat.