New Google Nest Thermostat and cannot setup sensor

[carboncow]

Hello,

I've got a blue wire system in my HVAC, it's a very simple setup for me with Y, W, R, G & C (blue). I've confirmed that C (blue) is attached on the module board of the NVAC in my furance too. 

My new Nest Thermostat (Charcoal) is working fine post setup but during the setup is stated there is no signal for a blue wire and this continues in the gear interface. 

What issues will this cause for me and any ideas why it's not being recognized. I see many others on the internets claiming similar issues. 

Thx. 

[CoolingWizard · Accepted solution]

The thought is that if you had the blue wire connected to Power common,  then  the nest would have best power solution.  

AC Cooling Wizard

[CoolingWizard]

@carboncow ,

What you need to confirm is that the blue wire is indeed attached to the Common side of the transformer that is feeding the R wire.  

AC Cooling Wizard

[carboncow]

Yes, the blue wire is attached to the terminal marked C in blue on the control module that the other wires are attached to with their respective colors. None are fed directly from the transformer as the low voltage side goes into the board first. 

[CoolingWizard]

@carboncow ,

can get a screenshot of your Nest backplate so I can see the wires attached?

AC Cooling Wizard

[carboncow]

I went to pull my photos from the HVAC control module as well as the back of the next and came across something I'm going to test latter. It seems there are two sets of wires...maybe old and new. The blue going to the connector on the HVAC control module looks to be a "grayer" blue then the one in the nest. I think the wrong wire may be hooked up and will report back later. 

Can you confirm what the blue wire does for the basic nest since everything seems to work as expected? 

HVAC Control MOdule Wiring 

Wiring on Back of Nest 

[CoolingWizard · Accepted solution]

The thought is that if you had the blue wire connected to Power common,  then  the nest would have best power solution.  

AC Cooling Wizard

[carboncow · Accepted solution]

update: We determined that someone had two full sets of wires hooked up to the HVAC module and the only the wrong one with the Blue "C". We swapped in the proper wire and now have constant power. This might explain while our very old Nest was temperamental at times. 

[Markjosephp]

Hello everyone,

I wanted to stop by and see how I could help.

Thanks for your help here, @CoolingWizard.

@carboncow, it appears that you have the Nest Thermostat 2020 model. To confirm, are you installing a Nest Power Connector or a Nest Temperature Sensor? If this is a sensor, it won't allow you to connect it in the Google Home app, as it is only compatible with the Nest Learning Thermostat or the Nest Thermostat E.

But I see that you have sorted it out. How's it going? Have you installed your Nest Power Connector correctly? If so, verify the Power Info in your actual thermostat's Equipment settings and ensure that its software version is up-to-date.

Let us know if you need more help.

Regards,
Mark

[Jenelyn_O]

Hi there,

I wanted to follow up if you still need help. Please let me know if you’re still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

I appreciate the help, @CoolingWizard and Mark.

Best,

Jenelyn