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Is your Nest Thermostat E showing error E195, “no power to R wire”? Mine did after six months of working fine. Here’s what fixed it.
I don’t have footage of the repair itself, but here’s exactly what happened and what the furnace tech did.
- A simple wiring fix
- No new thermostat needed
- I still really like the Nest Thermostat E
- Needed a furnace tech
- Came out of nowhere after 6 months
▶ Watch the full review on YouTube
What does Nest error E195 mean?
I went to adjust the temperature in the app and it said the Nest was offline with no power. At the thermostat, it showed error E195 and a little diagram showing the R (red) wire had no power.
Check the furnace first
I went down to the furnace, and the red R wire from the transformer seemed to be putting out plenty of power. A furnace tech came out, poked around and jumped the furnace. The furnace wasn’t the problem.
The fix: add a common (C) wire
The problem was the amount of current the thermostat needed. The R wire alone wasn’t enough.
The tech activated an unused wire in the bundle as a common wire. It’s often brown or blue apparently, and in my case the brown one was longer, so he stripped that one. We rewired it, flipped everything back on, and it worked.
Why did it suddenly happen?
I’m honestly not sure. I’d had it about six months with no issue until that night. It was a cold night, so maybe the thermostat was running more than usual, or a firmware update needs more power. I don’t know.
My advice: if your furnace is putting out power and no fuse or breaker is blown, and you’re not using a common wire, you might need one.Quick E195 troubleshooting checklist
- Read the error on the thermostat. E195 with the R-wire diagram means it isn’t getting power on R.
- Check that the furnace is putting out power on the R wire from the transformer.
- Make sure no fuse or circuit breaker is blown.
- If all of that checks out and you’re not using a common wire, you might need one, like I did.
For the record, I really like the Nest Thermostat E. It looks good with nice clean lines, and I’d had it about six months before this happened.
FAQ
What is Nest error E195?
It indicates no power detected on the R (red) wire.
How did you fix E195?
A furnace tech set up a spare wire (brown, in my case) as a common (C) wire, which supplied enough power.
Is the furnace the problem?
Not in my case. The furnace was putting out power fine.
Which wire becomes the common wire?
In my case an unused brown wire in the bundle. It’s often brown or blue, apparently.
Do I need a furnace tech?
I had one come out. He checked the furnace, jumped it, and wired the common wire.
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