If your Nest thermostat isn’t cooling, the most likely culprit is a wiring issue. I’ve found it’s usually mislabeled wiring, a loose wire or wires, or your Nest thermostat is missing a C-wire or Nest Power Connector.
The good news is that these issues are usually relatively easy fixes.
In this section, I’m going to go over some of the most common reasons why your Nest might not be cooling properly and how you can fix them.
1. Check Your Thermostat’s Wiring
The first thing you should do if your Nest isn’t cooling is to check the wiring.
In many cases, it’s a wire issue that’s causing a Nest Thermostat not to cool properly.
Start by ensuring that all the wires are securely connected and that there are no loose ends.
After that, move on to the next step.
Install a Common Wire (C Wire)
If your thermostat still isn’t cooling after you’ve checked the wiring, the next step is to install a common wire (also known as a C wire).
A common wire is necessary for most Nest thermostats, as it provides power to the unit.
If your Nest doesn’t have a common wire, it may not be able to properly power on and cool your home.
Fortunately, installing a common wire is usually a simple process that you can complete in just a few minutes.
If you have a C-wire, verify that all wires are connected to the correct thermostat connectors.
Take a picture of the wires from your old thermostat and use your thermostat wiring schematic.
If you can’t figure out your c-wire, I highly recommend that you hire a professional to help you out.
But what if you don’t have a c-wire? To protect your system and prevent any damage, make sure you turn off the power at your house’s fusebox, breaker, or main system switch.
You might find your furnace in a basement, attic, or less accessible area.
These are the steps to take if you feel confident accessing your furnace safely and have turned off all power to your entire home.
To ensure that your furnace is safe and accessible, you should contact a pro from your local area.
Install a Nest Power Connector (C Wire Alternative)
If you don’t have a c-wire, or if you’re not comfortable installing one, you can use a Nest power connector instead.
A Nest Power Connector is a small black box that provides power to your thermostat without needing a c-wire.
The power connector can be installed by you or a professional.
If you’re not comfortable working with wires, it’s best that you don’t try fixing your thermostat.
It’s better to be safe than sorry.
It’s easy to injure yourself when dealing with electricity accidentally.
Note: If you don’t have the C-terminal, you will need to contact a professional.
Before you begin
- Before you attach the power connect, finish installing the Nest thermostat.
- If necessary, update the thermostat.
- You don’t have to update if you own a Nest Learning Thermostat or Nest Thermostat E (3rd generation).
- Select the Nest Thermostat that you own. Go under Settings, then Version. You will need to upgrade if your version is before 1.1.
- First, be sure that the thermostat is in Off mode before you attempt to update.
- Go to Settings, then Version, then Update on your thermostat.
- Update 1.1 or higher
Update the wiring information if the C-wire in the app is not correct.
Home app
- Start the Home app.
- Tap and hold the tile of your device.
- Tap the Settings, then Thermostat, then Update, then Wiring at the top of your screen.
- Correct any wiring errors
Nest app
- Start the Nest app and then tap the Setting Nest settings icon.
- Tap on Thermostat, then Wiring, then Update wiring.
- Correct any wiring errors
Switch off the power supply to your HVAC system at your system switch or fuse box.
Doing so will prevent any damage and ensure your safety.
Turning the thermostat up can help you check that the correct breaker is off.
Wait a few seconds to ensure your HVAC system doesn’t turn on.
Incorrect Thermostat Wire Labels
I’ve had this issue before myself.
You think you have the wires in the right order, but it turns out you don’t.
This is a quick and easy mistake to make.
The easiest way to solve this problem is to take a picture of your old thermostat’s wiring before removing it.
That way, you can reference the picture when you’re installing your new
If your furnace is older, the thermostat wires might be labeled differently than what’s shown in your Nest app, and this can cause your Nest to not work properly.
Incorrect thermostat wire labels are usually caused by one of two things:
The thermostat was replaced before and the new thermostat uses a different wire labeling system than the old thermostat.
The furnace was replaced before and the new furnace uses a different wire labeling system than the old furnace.
If you’re not sure what’s causing the incorrect labels, I recommend that you hire a professional to take a look.
A professional can quickly identify the issue and make the necessary changes.
Ensure All Wires Are Connected
If you’re still having trouble with your thermostat not cooling, check to ensure that all wires are connected properly.
If any of the wires are loose, it could cause your Nest to not work properly.
To check the connections, remove the Nest base from its wall.
Gently pull on each wire to see if it’s loose.
If any of the wires are loose, gently push them back into place.
2. Confirm Your HVAC System is Compatible With Nest
If you’ve followed all the steps above and your Nest still isn’t cooling, it’s possible that your HVAC system isn’t compatible with Nest.
The best way to confirm compatibility is to use the Nest compatibility checker.
The compatibility checker will tell you if your HVAC system is compatible with Nest and if any issues need addressing.
If the compatibility checker finds an issue, you’ll need to hire a professional to fix it.
Once the issue is resolved, your Nest should work correctly.
3. Tripped Circuit Breaker
If your thermostat isn’t cooling and you have a tripped circuit breaker, it’s possible that the Nest thermostat is not getting enough power.
To fix this, you’ll need to reset the circuit breaker.
Once the circuit breaker is reset, your thermostat should start working properly.
4. Restart Your Nest
If your thermostat still isn’t cooling, try restarting your thermostat.
To do this, remove the Nest base from your wall and then press and hold the Nest logo for 10 seconds.
Once your thermostat has restarted, it should start cooling properly.
5. Reinstall Your Old Thermostat
If you’re still having trouble with your thermostat not cooling, you may need to reinstall your old thermostat.
Doing so will allow you to test to see if your HVAC system is working properly.
Moreover, you’ll be able to avoid damaging your system.
- First, shut off the power at your breaker or fuse box.
- Uninstall the Nest.
- Reconnect your old thermostat.
What to Do if It Works:
If everything works as it should, there’s likely a wiring issue with your Nest.
I’ve found that in these instances it’s usually because you need a C-wire or Power Connector.
Again, I recommend letting a professional install these for you.
What to Do if It Doesn’t Work:
You hooked up your old thermostat, but your system still isn’t working properly.
Your HVAC system likely requires maintenance.
Call a pro to have them provide the service you need.
Summary
Nest thermostats are a great way to save money on your energy bill.
However, if your Nest isn’t cooling, it can be frustrating.
If you’re having trouble with your Nest not cooling, I recommend that you follow the steps I’ve outlined in this article.
By following these steps, you should be able to fix the issue and get your Nest working properly.
I hope you found the solution you needed in this guide.
Always use caution when working with the wiring on your Nest thermostat.
Remember, don’t hesitate to reach out to a professional if you’re not comfortable fixing your thermostat on your own.
Frequently Asked Questions
Why is my Nest not turning my air conditioning (AC) on?
There are a few different reasons why your Nest might not be turning on your air conditioning.
The most common reasons are incorrect wiring, an incompatible HVAC system, or a tripped circuit breaker.
If you’re having trouble with your Nest not turning on your AC, I recommend that you follow the steps I’ve outlined in this article.
By following these steps, you should be able to fix the issue and get your Nest working properly.
How do you force Nest to cool?
If you want to force your Nest to cool, you can do so by setting the temperature lower than the current temperature.
You’ll need to hold down on Temperature and select when you want the preset to hold.
By setting the temperature lower than the current temperature, your Nest will turn on the air conditioning and start cooling your home.
