Blue wire not connected. only Red, Green, White and Jumper

[mlitt562]

Hello all welcome the feedback/solution

Ran the compatibility checker for a third gen NEST learning thermo. All times result was fine, system would take.

My AC tech also told me a 3rd gen Nest learning would be fine. We have been able to hook it up but unable to get it to detect the AC.

Photos of old and new thermo hook ups. the Blue wire is not connected as it wasn't prior. In reading through some comments, it appears I need to check my control panel of my furnace which I have. 

Can someone please help as I am confused as to why the Nest will not detect the AC. No errors are detected but the Equipment option on the NEST thermo only shows the fan heat and power. help please.

TIA!

New wiring. there is paint on the wires but the red is in RH (little red on the end near the connector)CP for the Furnace -Old Thermo wiring

[Arose]

Jasonroze

[mlitt562]

Can anyone please assist or provide another site to resolve? I can call my HVAC tech though would rather figure this out on own. TIA

[MelbaDT]

Hey folks, 

Sorry for the delay but thanks for reaching out and for these photos, mlitt562. 

I'm afraid that if there is an AC function of your HVAC system, there should be a wire connected to the Y or OB terminal should you have a heat pump. Are you comfortable tracing where is the blue wire connected to on your control board?

Best, 

Melba

[mlitt562]

Thanks for the response. I had forgotten about this as I couldn't wait on a solution. I texted my AC company and was provided the proper wire to connect. In my case it was the blue wire to Y1 and that solved it. I would encourage anyone who is struggling to call their AC repair/maintenance folks for help when you are unsure about the wires and not to try to figure this out on your own as it can be dauting.  My Blue wire was not connected on my previous thermo.  Even though the Nest documentation states to not connect wires that were not previously on your thermo,  I needed to so I would also encourage the Nest PMs to double check your technical writing - not always the case.....

[MelbaDT]

Hey there, 

Thanks for getting back to us and for sharing what you've done to have it working as it should. We'll also ensure that we'll let our team know of your feedback. 

Feel free to let us know if you have any further questions in mind. 

Cheers, 

Melba

[Jeran]

Hey mlitt562,

We haven't heard back from you, so I'll go ahead and lock up this thread in 24 hours. Thank you for coming back with your feedback!

Thank you for your help on this, MelbaDT!

Best regards,
Jeran