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O and B wiring help please! 😬

CO_AZ
Community Member

Trying to help set up my grandma's Nest in AZ and running into trouble. Old thermostat has O,B,W,G,RH wires. I tried connecting B to the C and the O to the O/B as others had success with. I received an error from Nest looking for the Y and moved the W to the Y. When we turned it on, instead of AC it was blowing heat. Help!!

 

5 REPLIES 5

CO_AZ
Community Member

Nest tech help had me rewire back the W to original place. But then received the error code E77 looking for a Y1 wire. I contacted support again and they stated I need to have a dedicated Y wire added. It's there an easy fix to this without calling a specialist?

Subiewrx22
Community Member

Do you have a picture? Also do you have a yellow wire. 

CO_AZ
Community Member

I do have a yellow wire and a picture: https://photos.app.goo.gl/VoFm8sjPH8QFnEhL9

It is a heat pump system. I've also tried moving the yellow wire to Y but when turning on the AC all we had was the fan and no cooling. 

 

 

Subiewrx22
Community Member

zoeuvre
Community Specialist
Community Specialist

Hi folks, 

 

Thanks for chiming in, @CO_AZ

 

@Subiewrx22, oh no! Let's see what's going on.

 

Are you located in North America or Europe? What type of Nest Thermostat do you have? Since you have a heat pump heating system, your thermostat wires should be wired as follows: 

 

  • Yellow wire to W or W1
  • Green wire to G
  • White wire to OB or *OB
  • Blue wire to C
  • Red wire to R or RH

 

Let us know how it goes.

 

Best,

Zoe