Nest Learning Thermostat lost power

[DQz]

My Nest Learning Thermostat Gen 1 lost power - about 3 hours ago.  Has been installed for about 8 years without problems other than wandering temp settings.  

The initial message is "no power to the RH wire, so I put a volt meter on it and was surprised to see it measuring 27v.

Tracking down the error message "E2" through the support link it asked me to check the breakers on the unit  - all normal.  I reset anyway - no change in error message.  The thermostat wires are connected to the heater/air handler up in the attic.  I checked the connections and saw no loose connections or evidence of damage or rust.  

    -is a factory reset of the thermostat of any use?

    -is the Nest itself likely to be the fault, or is this exclusively a wiring problem?

Not an HVAC guy, so any help on next steps appreciated.

[Markjosephp]

Hello DQz,

Thank you for taking the time to let us know about your inquiry. Let's sort this out.

It appears that your system might not provide enough power or any power to either the thermostat or a specific wire. Please check this out:

• Get the power status from Battery Level, Voc, Vin, and Lin under Technical Info.
• Make sure that the breakers are on.
• Ensure all the wires are properly connected.
• Check the air filter. A clog in the air filter can limit how much air flows over the cooling coils. If the clog persists, the cooling coils can freeze, causing the system to shut off.
• Check the fuse for your HVAC system. If the fuse burns out, the system might cut off the power to the thermostat and cause an E2 wiring report.

Keep us posted.

Regards,
Mark

[Markjosephp]

Hey there,

I don't want to be a nudge, but I'd like to check if you were able to get your thermostat working again. Feel free to reach back if you still need help.

Thanks,

Mark

[DQz]

replying to my own post in case it might help someone with a similar problem.  After above steps in original post failed to resolve issue I bought a new nest thermostat - cheapest non learning model, and hooked it up.  I provided a DIFFERENT error message - said the Y wire had no power.  SO I went up to the attic and checked the Y wire, and discovered it was connected to a float switch under the unit, in the emergency drip pan, which was full of water, and had tripped the float switch, thus depowering the unit.  While things like a condenser coil might have been the cause of the excess water it turns out to have been the simplest (and non electric) problem - the drain line for the drip basin was plugged.  Cleaning this out solved all problems.  Learned more about AC units than I wanted/expected to this week

[Markjosephp]

Hi DQz,

Thanks for posting and for keeping us in the loop on what you've done to have your concern rectified—give yourself a pat on the back for a job well done!

So I will lock the thread within 24 hours unless I can help out with anything else.

Best regards,

Mark