3rd gen learning thermostat not turning on

[crimeariver]

Hi, 

I did install a Nest thermostat for the first time, but it does not turn on. 

1. It is compatible: Checked the guide at least three times. I have a relatively modern furnace + ac and existing thermostat with 5 wires (Y W R C G). The guide tells me to use Y1 W1 Rh C G. 

2. Device powers on via USB, but when I then put it on its base it says its going to restart and then does not power on.

3. Wiring checked multiple times and I moved back and forth to my old thermostat ok. Old one works, Nest not a blink ever. 

How to troubleshoot? 

[Patrick_Caezza]

@crimeariver 

Post a picture of the original thermostat wiring.

[crimeariver]

@Patrick_Caezza thanks for the quick reply, but I did get it resolved by disconnecting the blue wire C as it is optional. 

How it is not in the default troubleshooting for setups with C wire. It has to happen to many people before. 

[Patrick_Caezza]

@crimeariver 

I don't consider the C wire optional, even though Google Nest has always claimed their thermostats can work without it.

The C wire will rarely cause a problem, and when/if it ever does, it can mostly be traced to other problems.

In the end, if it is working to your satisfaction, then that is all that matters.