E Nest Thermostat does not detect W1 wire and show E155 error

[obeperalta]

Hi, I have an E Nest Thermostat working properly for some years and suddenly appears the E155 error code. Te connection diagram showed as the W1 wire was not conected.

Following the many troubleshooting procedures, i checked:

-The correct wire connection and continuity, the 24 volt tension, and any possible whater content anyware.

As i have another thermostat in the house (a 3r generation one) i interchange them and as a result y verify that the 3r generation connected with the same wiring than the E, works normaly and detect correctly the W1 wire

So it seams that the E thermostat or his baseplate are damage? is it correct? is normal to occur this? is possible to repair it?

If someone can help me i will appreciate!!!!

Regards Daniel

[humbertogarcia]

Hi obeperalta,

Thank you for posting in the community! I want to commend you on your incredibly thorough and logical troubleshooting. By swapping the units and identifying the working components, you have taken a crucial step that has given us a very clear picture of the situation.

Based on your excellent troubleshooting, here is a direct answer to your questions:

• Is the E thermostat or its baseplate damaged? Is it correct? 

Yes, your conclusion is correct. The E155 error, combined with the successful operation of the 3rd-generation thermostat using the exact same wiring, strongly indicates an issue with the Nest Thermostat E or its baseplate. You have successfully diagnosed the problem.

• Is it normal for this to occur? 

No, this is not a normal or expected occurrence. Nest thermostats are built to last, and a hardware failure of this kind is a very rare event.

• Is it possible to repair it? 

Please consider that Nest thermostats are not designed for user repair because of their intricate internal components.

For any additional assistance, don’t hesitate to contact me.

Regards,

Humberto

[obeperalta]

Hi Humberto, thanks for the replay!

I understand that the baseplate in not possible to be repaired by the user but my question pointed to be repair for an autorized deler. Is it possible or the recommendation is to dispose it?

Regards! 

Daniel

[humbertogarcia]

Hi obeperalta,

Thank you for sharing your concern about the Nest Thermostat E baseplate. 

The team would like to learn more about this situation. When you get a chance, please fill out this form and let me know when you’re finished. We’ll have someone reach out to you via email from there. 

Please make sure to provide this thread identification and your community username in the corresponding fields.

For any additional assistance in the meantime, feel free to contact me.

Regards,

Humberto