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5 wire single fuel heat pump and AC system - no AC

Community Member

Installed Nest learning thermostat (from Costco) plugging color coded existing 5 wires into the Nest. This is a single stage heat pump, single fuel (electric) system which has air handler (Lennox) and exterior AC unit.

Turn on AC on Nest and air handler turns on (blows air), but air is not cold (works fine with original thermostat so AC is functional). AC unit compressor fan (exterior) does not power up.

Existing wire to Google Nest installation:

Yellow to Y1

Green to G/G1

Red to RH

White to W1

Orange to O/B

What am I doing wrong?


Community Specialist
Community Specialist

Hey there,
Sorry for the late response, but I wanted to drop in here to help.

I understand that these issues can be confusing but I definitely wanted to stop by and see how I could help.

Just wanted to double check to see if you were still needing help on this? If so, what troubleshooting steps have you tried?

Please let me know.

Best regards,
Garrett DS

We've since returned the thermostat. I tried every possible configuration I could come up with but determined for right or wrong, that without a common wire the unit will not function properly in this situation. I check my setup on the competitor's website and it indicated that a common wire will be necessary. It's not a Dual Fuel/Hybrid unit or anything fancy. Just AC and heat pump (blower in garage, heater in attic and AC outside) I've confirmed since that the common wire was pulled through to the wall (but not attached) so I presume it needs to be connected at the main panel which hopefully, when I get to it, is in the air pump unit in the garage which is easily accessible vs. crawling through attic to find heating unit.


Community Specialist
Community Specialist

Hey all,


It has been a few days since the last reply, and I am going to lock the thread at this time. If you have any questions, please feel free to create a new post. 

Best regards,