The short answer
When a Nest thermostat in Northern Virginia says “No power to Y1” or “No power to W1,” the wire that turns on the cooling or heat pump (Y1) or the heat (W1) has gone dead at the system end. On the Y1 version, Google’s own label is often “cold weather shutoff”: a safety switch on the air conditioner tripped to keep it from running in the cold, and the system may need maintenance. On a heat pump, that same wire runs your heat, so in winter it’s a no-heat problem.
What W1 and Y1 are
W1 is the wire that tells a furnace or boiler to heat. Y1 is the wire that starts the outdoor unit: an air conditioner in summer, and on a heat pump, heating and cooling both. The Nest powers W1 from the Rh side and Y1 from the Rc side, and it watches each one. When the system end stops answering, it says so.
Don’t mix this up with W1 on a Wi-Fi screen. W1 through W5 are Wi-Fi codes about the internet connection, not the W1 heating wire.
Swipe to see all columns →
Swipe to see all columns →
| Code | What Google says it means |
|---|---|
| E12, E32, E82, E162 | No power to W1 wire |
| N3, N23, N73, N153, N403 | No power to W1 |
| E10, E30, E66, E80, E116, E160, E196, E296 | No power to Y1 wire (cold weather shutoff) |
| N4, N24, N74, N154, N404 | No power to Y1 |
| N262, N263, N412, N413 | In extremely cold weather only: no power to Y1 (cold weather shutoff), the system needs maintenance |
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The cold weather shutoff
Google’s explanation for the E10 family: the air conditioner has tripped a safety cut-out switch that keeps it from turning on in very cold weather, and the system might need maintenance. On a straight air conditioner in November, nobody needs cooling, so it’s not an emergency. It’s still worth having looked at before spring, because a tech wants to know why the switch opened, and refrigerant pressure is usually where that starts.
A heat pump is different. Y1 runs the compressor in heating too, so a dead Y1 in winter means the outdoor unit isn’t heating. If the backup heat strips are carrying the house, you’ll feel it on the electric bill first. Aux heat and emergency heat explains what the Nest shows while that happens, and a heat pump covered in ice is a different problem with its own fix.
Other reasons W1 or Y1 go dead
- A loose or broken wire, at the Nest base or at the terminal strip on the furnace or air handler. Common after a new thermostat goes in or after work near the furnace.
- A float switch on a clogged drain, wired into the cooling circuit so it opens Y1 on purpose before water hits the floor. A drain cleared with a trap and switch runs $175 to $420.
- A failed contactor, the relay that powers the outdoor unit. Replaced, $290 to $425.
- On the heat side, a control board that isn’t passing the call to the burners. Replaced, $550 to $1,180.
What you can check
- Turn the system off at the breaker, pull the Nest off its base, and make sure the W1 or Y1 wire is pushed all the way into its connector. Turn the power back on.
- Look at the drain pan and the condensate pump. Standing water means a float switch did its job.
- If the wiring changed recently, compare it with the setup diagram from when the Nest went in.
- On a straight AC in winter, a cold weather code can wait for a visit. On a heat pump, it can’t.
When it’s a call
- No power to W1 and no heat.
- A Y1 code on a heat pump in heating season.
- Water in the pan you can’t clear.
- N262 or N413: Google itself says the system needs maintenance.
When we come out for a Nest code, the technician checks the whole system, not just the thermostat: the equipment, the wiring at both ends, the filter and the drain. The diagnostic is a flat $99, the repair is priced in writing before anything starts, and if the problem really is the thermostat, we say so. On a heat pump, heat pump repair covers what else we check.
Every Nest code is on our Nest error code list. No power to Rh is a different code with different causes: the E74 post.
Code meanings and on-screen messages are Google’s, from its Nest help pages: error codes. Last checked November 10, 2026.
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Questions people ask
What does no power to Y1 mean on a Nest thermostat?
The wire that starts the outdoor unit isn’t getting power back from the system. In cold weather, Google often labels it a cold weather shutoff: a safety switch on the air conditioner tripped. On a heat pump, Y1 also runs the heat.
What is the cold weather shutoff on a Nest?
Google’s name for the E10 family and N262, N263, N412 and N413. The air conditioner tripped a safety switch that keeps it from running in very cold weather, and Google says the system might need maintenance.
What does no power to W1 mean on a Nest?
The heating wire isn’t getting power back from the furnace or boiler. Usually a loose or broken wire at either end, or a control board that isn’t passing the call.
Is W1 on my Nest a wiring problem or a Wi-Fi problem?
It depends where you see it. “No power to W1” in an E or N code is the heating wire. W1 through W5 on a Wi-Fi screen are Wi-Fi codes about the internet connection.
