Cooling stopped working on Nest 2nd Gen - E30 error

[Falconet9]

I have a 2nd Gen Nest Learning Thermostat (2013 purchase date) that has been hooked up to my newer AC/Heat for well over a year and everything has worked without an issue. That said I don't think there is a wiring connection issue.  Then today I started receiving an E30 code error. "No Power to Y1 Wire Detected". So I started to do some trouble shooting...

When I take the Learning unit off the wall, it continues to light up and connect to the nest app. One of the troubleshooting things is to replace the battery... if it lights up and connects would that mean the battery is working well enough to allow the unit to see my AC?

I switched the learning unit out with a brand new Nest Thermostat (the cheaper one). Once I plug everything in and flip the circuit breaker,  of the sudden the AC is available and working again (so at least the AC unit itself is working and does not seem to have an issue connecting to a thermostat).

I rewired the Learning Unit again and... no AC. The heat seems available, so no issues there (yet).

Any ideas on what my problem could be? Is the Learning unit AC just... dead? (Yikes!)
Thanks!

[Falconet9]

I did some more looking - The Learning 2nd Gen unit sees the Y1 wire is connected, but only senses equipment on W1.

[Falconet9]

So no ideas?

[aperezdeleon]

Hi Falconet9,

Thanks for reaching out to our community.

I understand how confusing it can be to determine whether your system is malfunctioning or if the thermostat needs adjustment to cool your home. Don't worry, I'm here to assist you.

Once you connect your Nest Learning Thermostat, what are you able to see on the equipment screen? Is your Y wire not being detected, or does it say it doesn't have power on it? My suggestion would be to turn off the breakers, ensure that the Y1 wire is making a proper connection with your thermostat, and re-strip and secure it properly on the base.

I also suggest checking the base itself, as there's a possibility the wire might have broken inside the terminal of your thermostat, which could make it difficult to get a consistent connection with your cooling equipment.

Have you received any notifications or emails about when your thermostat started showing this error code? It would be helpful if you could also tell me what other wires are connected to your thermostat.

Please let me know what you find out.

Regards,
Angel.