Warm To Touch - Nest Learning Thermostat - 2nd Generation T200577

[Craiggers]

Bought this in 2013 - Nest Learning Thermostat - 2nd Generation T200577

I only called this cooling issues because I'm in Florida, it is hot, and I have no other good choice.

The A/C system I'm using had a few power stops and starts recently which may have triggered the behavior.

Last few days the temp shown on thermostat was higher than it felt.  Now it says 90 when I know it is 77 or so.

When cup my hand over thermostat it is slightly warm.  When I pull it off the wall the back side is even warmer and the wires behind the thermostat are warm.   But, after taking it off, it cools down -- however, temp still reads high right away on power-on.

I read another comment that the Nest team had the customer turn off wifi so I'm trying that now.  At least I will eventually know if wifi chip is heating things up.

I have a new 3rd generation on order to replace.

My 2nd generation thermostat is hooked up to a 2yo 2 Stage A/C.   Never had a thermostat issue in the past.

I'd prefer 20 but 9 years of performance is not too bad.  I'm sure I've saved much more than that and the house is much more comfortable than it would have been without a Nest thermostat -- so I'm not an unhappy camper.

I see some people replacing their batteries but I have no low power alert -- the thermostat acts fully functional.

I get 3.8 on the battery and 100 MA on the line charge (watched a youtube video on what to look for).

I have tried the reset selection and I've held for 10 sec until it blacks out and restarts -- no change in the high temp listing.

Any advice or suggestions?

[CoolingWizard · Accepted solution]

This sounds like a component of the nest circuitboard or battery is failing.  This high resistance is what is generating the heat.  This heat is radiating to the temperature sensors and that is the source of your false reading. Sadly, this thermostat is at end of life.  

[Jeran · Accepted solution]

Hey there Craiggers,

I'm sorry about the delayed response, but did you have any more questions or need any additional help? 

Thank you,
Jeran
 

[CoolingWizard · Accepted solution]

This sounds like a component of the nest circuitboard or battery is failing.  This high resistance is what is generating the heat.  This heat is radiating to the temperature sensors and that is the source of your false reading. Sadly, this thermostat is at end of life.  

[Craiggers]

Hot spot was on Y1 / Y2

For a little follow-up I followed the hot spot, from Y1/Y2 buttons to the PCB inside.  I found no discoloration but I found a metal cased capacitor just north of Y1.  

That was a 2nd Gen.   I went to Home Depot and bought a 3rd Gen and, with the exact same wiring, I have no heating issue.

I had an A/C guy come out and he checked the voltages and said everything on the air handler was as expected.


It was only this plastic mount  that was heating, the thermostat itself seemed to reflect properly -- as when I let the thermostat fully cool off, when plugged back in it would slowly creep up to 90F.

Thank you so much for the comment that helped me decide what to do.

I think the thermostat itself is still good, but for how long?

[Ryan_G]

Hey there,

Thanks for being here in the Google Nest Community. 

I'd like to bump in here and make sure that you’ve seen our response.
Please let us know if you have any other questions or concerns as I will be locking this thread in 24 hours.

Have a great day.

Best regards,
Ryan
 

[Jeran · Accepted solution]

Hey there Craiggers,

I'm sorry about the delayed response, but did you have any more questions or need any additional help? 

Thank you,
Jeran
 

[Ryan_G · Accepted solution]

Hey everyone,

I'd like to jump in here and check if you've seen Jeran's response. Let us know if you need more help by replying to this thread.

Thank you for your help, Jeran.

Regards,
Ryan 
 

[Craiggers]

Thanks! Ryan Thanks Jeran!