How To Fix Your Nest Thermostat If It Has No Power

If your Nest Thermostat is a few years old, it may lose power suddenly. But there is no need to worry as this is a normal issue after a few years of use, and we’re here to help.

The following guide walks you through fixing a Nest Thermostat in three situations: whether the thermostat shows a red, green, or no light.

Quick Summary –

No Light on Nest Thermostat– Check if the display is connected and properly aligned with the base. – Check if the system gets power from the source.- Check the compatibility of the power source with the Nest thermostat.- Check the wiring.- Check the fuse.- Reconnect or replace the battery.- Contact a professional if needed.
Red Blinking Light on Nest Thermostat– During Installation: wait for the battery to charge, or speed up the charging using a USB cable. Check to wire if blinking persists. – After Long-Term Use: check wiring or power supply.
Green Blinking Light on Nest Thermostat– Reconnect the display and check the connector pins.- Press and hold the thermostat display for 10 seconds to restart it if it’s frozen mid-update.

No light

If your thermostat isn’t showing any light, the battery cannot supply any power to the thermostat. It may be because the battery is dead. Here’s how to fix the thermostat if this is the case.

Check If the Display is Connected

The display has to be properly connected to the base for the battery to change. If it’s not, the thermostat won’t turn on.

Pull the display off the base to fix the issue and ensure no wires keep the display from connecting to the base. Now,  line up the connectors on the base and the display and press the display so that it is set. You’ll hear a click when the display is properly connected to the base.

If you see a blinking red light after this, the thermostat will charge and turn on in a bit.

Check If the System is Getting Power

power system

The problem may be the power source. Try turning the breaker off and on again, and see if the thermostat turns on. If you supply power to the thermostat via a fuse box, see if it is still intact and replace it if it’s blown.

If doing this makes the thermostat blink red, it’s charging and will turn on once it has enough charge.

Check the Compatibility

nest equipment detected

If you installed the thermostat and it’s not turning on, it may be due to a power incompatibility. Nest Thermostat works with most 24 V systems.

The thermostat won’t charge the battery if connected to a lower-voltage power source. On the other hand, if it’s connected to a higher voltage source, it may damage the thermostat.

For more information about power compatibility, check your manual.

Check the Wiring

Before troubleshooting, you should always check your wiring. If a switch is misaligned or a wire is ripped, burnt out, or loosely connected, fix it before turning on the thermostat and checking the power again. 

Check the Fuse

If the wires are okay, and you’re still not receiving any power on your thermostat, you might have a fuse problem. Start by removing the thermostat’s cover and checking for a fuse. A fuse is a glass tube with a metal end. Also, check the string running inside the fuse and filament. Replace the fuse if the glass tube or filament is broken.

Before you Start…

Reconnect the Batteries

If a battery powers your thermostat, there is a huge chance your thermostat has no power due to the battery. Start by removing your battery and putting it back to ensure that they are placed properly. (2)

Replace the Batteries 

The majority of people forget to replace batteries frequently. For the best performance of your thermostat, you should replace the batteries after every six months at least. Therefore, if your thermostat has no power, you can replace the old batteries with new ones to ensure that your thermostat isn’t off because of a non-functional battery. 

Contact a Profesional

nest thermostat

If all these DIY techniques aren’t working for you, then it’s time to bring in a professional and highly-trained HVAC expert.  Based on the thermostat’s condition, they can fix or replace it. 

In general, a blinking red light indicates a low battery, a blinking green light indicates a software update or startup, and no light indicates that the thermostat isn’t receiving any power.  

You may want to check the learning guide on the Nest thermostat that isn’t working after a power outage. Un

Red Blinking Light on Your Nest Thermostat

red light

A blinking red light on your Nest thermostat indicates that the thermostat battery is very low but is being charged. The troubleshooting procedure depends on the conditions under which the light blinks.

During Installation

If the blinking red light is on during installation, the thermostat will need a few minutes to charge before it turns on. It can, however, take up to an hour for the thermostat to turn on if the battery is extremely low.

You can accelerate the charging process using a separate USB cable. If you pull the display off, you’ll see a USB port. You can use a USB cable and a USB wall charger to charge the thermostat faster.

If the blinking keeps returning, there may be a wiring issue. Check whether the connection wire is intact and properly connected to the power source.

After Long Term Use

thermostat longterm use

If the red light blinks after using the thermostat for a while, there may be an issue with the thermostat wiring or the power supply. If the blinking red light doesn’t go away, check the wiring and see the thermostat power connection is intact. (1)

til our next article!

Green Blinking Light on Your Nest Thermostat 

green blink light

A green blinking light on the top of the thermostat can mean one of three things: 

  • The thermostat is updating its software
  • The thermostat is starting up
  • The thermostat is restarting

The thermostat may have frozen mid-update if the green light blinks for over 15 minutes. You can try the following if this is the case.

  1. Pull off the display and reconnect it. Line up the pin connector correctly before you push it. When it’s perfectly and correctly seated, you’ll hear a click.
  2. If the green light still doesn’t turn on, you can resort to the oldest trick in the book to fix any computerized device. Press the thermostat display for 10 seconds. When you release it, the thermostat will automatically restart and be restored to its pre-update state.

(1) power supply –
(2) battery –

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