Two zone system - AC and fan in zone 2 not working

[Smoathly]

2 zone HVAC system. During winter, installed 2 Nest Thermostats (with power connectors). Heat worked perfectly fine. Just started AC season. Zone 1 is working fine. Zone 2 - nothing. System doesn't kick on, fan doesn't turn on.

Restarted and then did a reset of thermostat - problem remains.

May or may not be relevant - fan only function does not work for either thermostat.

suggestions appreciated...

[Patrick_Caezza]

Are both of the thermostats wire the same?

Can you post a picture of the zone controller wiring?

Where do you have the Power Connectors installed? Between the zone controller or elsewhere?

[Smoathly]

Yes. Both the thermostats are wired the same. The Power Connectors are installed at the zone controller (one Power Connector for each zone). I tested the old thermostat on Zone 2, which did not fix the issue. I'll post a photo of the zone controller when I have a chance. Thanks.

[Smoathly]

Hope this photo helps.

[Patrick_Caezza]

If you installed the original thermostat and it still has the problem, then it's not the Nest.

I noticed that each zone thermostat has a C terminal, why are you using the Power Connectors?

How did you wire the Power Connectors?

Do you know what size the 24Vac transformer is? 40VA or 75VA

[MelbaDT]

Hey folks, 

Thanks for your responses, Patrick_Caezza. 

Smoathly, I want to jump in to ensure everything is covered here. How's it going now with your Nest thermostat? Should you still need help with it, please provide the answers to the questions above so we could continue the ball rolling. 

Best, 

Melba

[MelbaDT]

Hey Smoathly, 

Checking back in should you still need our help. Let us know by replying to this thread. 

Best, 

Melba

[Smoathly]

Hello. I left for a business trip and didn't have a chance to update. Still need to resolve this issue after I return from the trip. I'll update as soon as I can.

Thanks.

[MelbaDT]

Hey there, 

Got it — thanks for getting back to us. Keep us posted then as soon as you're able to. 

Best, 

Melba

[Smoathly · Accepted solution]

Well, after returning from a business trip, I was able to work on this issue again. After a lot of time troubleshooting with Google Nest (thank you for your assistance), wiring was determined to be the issue. Before calling for a technician, I took another trip around the wires focusing on the Power Connector. Lo and behold, the Y connection, which looked solid, was just loose enough to be the cause. Thank you Patrick_Caezza and MelbaDT for your advice. And thanks to Google Nest support as well.

[MelbaDT]

Hey Smoathly, 

You're welcome and thanks as well for getting back to us and for keeping us in the loop of what had resolved your concern. We're glad to hear that your thermostat is now working as it should — give yourself a pat on the back for a job well done!

Cheers, 

Melba

[MelbaDT]

Hi, 

We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.

Best, 

Melba