HomehealthNest Thermostat not Cooling (You MUST Double-Check The Wiring)

Nest Thermostat not Cooling (You MUST Double-Check The Wiring)

Are you having problems cooling your Nest thermostat? There are several reasons your Nest thermostat might not be cooling properly, or worse, it could be blowing hot, when it should be.

Regardless of your choice, it is important to begin by diagnosing the problem.

How to fix a Nest Thermostat that isn’t cooling

Your Nest thermostat isn’t cooling because your wiring was incorrectly labeled according to the “Conventional”, instead of the “Heat Pump”, side. This can be fixed by renaming the wiring from the old thermostat using the Heat Pump side, and wiring your Nest accordingly.

Thermostat wires are incorrectly labeled

You might be able to mislabeled your wires if you think you’ve misidentified your cooling unit.

Correctly identify Your Home Cooling Systems

The first thing you should do is to confirm which type of cooling system your home has.


This is easiest to do by checking your outside system. It should have a label that indicates whether the unit is an air conditioner, heat pump, etc.

You can also get the model number and brand name on the device by going to Google.

Another excellent tip for investigating is to turn on your heat and check if the outside system turns on. If it does, that is a sign you have a heat pump.

Since you are experiencing Nest cooling problems, my guess is that you have a heat pump system, but didn’t realize it was conventional.

Relabel old thermostat wiring

Now that you are certain about the type of cooling system you have, you will likely need to rename your thermostat wires.

You should have a photo of the wiring arrangement for your thermostat. You can refer to that image to re-name your wires using Heat Pump row (for instance).

Once you have your wires labeled correctly, you can open Google’s Nest thermostat compatibility checker to enter them.

This information will be used to automatically generate the Nest wiring that you need in order to set up your device.

Rewire Nest Thermostat

Make sure your Nest is off-line before you begin wiring it. This will ensure that you are able to safely and effectively work on the wiring.

Next, remove the Nest’s display screen and start disconnecting and reconnecting appropriate wires using the diagram that the compatibility checker generated in the previous step.

After all Nest wires have been connected in the correct places, ensure that they are secure.

After you are done, turn off the circuit breaker and replace the Nest display screen.

Your Nest may take a while to restart, but once it does, your cooling problem should be resolved!

Tripped Circuit Breaker

You can check your circuit box for a trip breaker if you still have cooling problems.

It is simple to do. Just look for switches in the off position.

Once you have identified the breaker, turn it on and off, then flip it to the on position.

This will reset the breaker, and could resolve your problem.

RC, RH Wiring Issue

Older thermostats may have one R wire that is connected to an RH or RC wire by a piece metal. It is easy to overlook.

Nest separates the RC wires from RH wires. Nest will accept one R wire if you have it.

If this doesn’t resolve your problem, then connect the red wire to the RC port and see if it does.

Blown fuse inside air handler

A blown fuse in your Nest cooling unit could also be a reason why your Nest cooling system isn’t functioning.

It can be difficult to reach this fuse. You may need to remove many screws in order for the cover of your air handler to come off.

Fuses are very inexpensive, so you don’t have to worry about which one you have blown.

Other Troubleshooting Ideas

These are the last things you can do if you have cooling problems.

Check Nest Compatibility With Your Cooling System

It’s possible that your cooling system is not compatible with Nest.

The Nest doesn’t work with solid fuel or high voltage systems. The Nest might not work with your home cooling system, depending on how you use it.

This determination should be easy thanks to the investigative work that you have done.

Here’s a list of compatible systems with Nest thermostats from Google

Start the System

Although it’s unlikely that this will resolve an issue as serious as your Nest thermostat not cooling down, it’s worth doing a reset.

This can be done by turning off or cutting off power to the Nest in another way. You just need to make sure it is completely off.

Wait for five minutes before turning on the Nest again.

Wait for the Nest to reboot, and then wait for a few moments as it reconnects with your home’s systems.

Alternatively, you can manual reset directly on your device.

  1. To open Quick View, press the thermostat ring.
  2. Select Settings.
  3. Set the ring to , then press the button to select.

Install Your Old Thermostat

If you have reached this point but still experience cooling problems, you will want to check with Nest to see if the Nest is the problem.

Reinstalling your thermostat is one way to accomplish this.

You’ll need to turn off the fuse in the thermostat first before touching any wires.

You can check if there is a problem with your wiring by replacing your thermostat. If the Nest is not working, it could be the thermostat.

If the thermostat doesn’t work, it could be that the wiring to your cooling system is not working properly. A professional electrician will likely come to your home to inspect the wiring.


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