Is your Nest Thermostat Not Cooling at Night? (7 Actionable Steps)

Are you waking up in a pool of sweat because your AC isn’t working again?

Maybe your Nest thermostat is to blame.

Don’t worry – there are a few simple things you can do to fix your faulty cooling system.

Here are 7 steps to fix your Nest thermostat not cooling at night:

1. Reset the schedule on your Nest thermostat.
2. Turn off the power for the HVAC system and back on.
3. Check and fix the wiring in your Nest thermostat.
4. Check and repair your AC.
5. Check your AC drain pan and Drain Lines.
6. Replace the battery on an older nest model.
7. Have your utility company remove the electricity-saving box.

If you don’t feel like a HVAC Technician that has to know everything about his smart thermostat, please continue reading as I will break down every step of the way so you don’t have to call a professional

Let’s get started!

1. Reset the Schedule on Your Nest Thermostat

The Nest thermostat is a phenomenal piece of tech.

It can learn what temperatures feel comfortable to you and will ensure that it stays within that range.

However, there’s a chance that the Nest thermostat has scheduled your nighttime temperature incorrectly, or it was affected by a bug.

Whatever the case, resetting the schedule is the most straightforward fix that you can try. Here’s what you do:

1. Open the thermostat’s Settings.
2. Go to Reset and select Schedule.
3. Press Reset (or Clear other Nest models).

Your Nest is now ready to create a new schedule for your hot summer nights.

2. Turn Off the Power for the HVAC System and Back On

With modern technology, you’d think that everything would work all the time. 

Unfortunately, even with the newest thermostats and AC units, we sometimes have to resort to the “turn it off and back on” trick.

This trick will fix your issue regardless of what device is causing it.

First, Locate your breaker box and turn off the power to the HVAC.

You should do the same for the thermostat too.

Then, leave it off for a few minutes.

Check the lights on your AC to ensure it’s off because it might still have some power left.

If you have a generator, turn it off.

After 5-10 minutes, turn the power back on.

Adjust your thermostat and check if the problem persists the following night.

3. Check and Fix the Wiring in Your Nest Thermostat

Incorrect wiring in the thermostat can often cause issues.

There’s a chance that you didn’t even notice there’s a wiring issue because it worked fine throughout winter.

However, if the AC won’t work with the thermostat, it’s usually because of incorrect wiring.

Wires can get shorted and won’t work as intended.

Bad wiring won’t always cause issues at first.

It might work for a while – but then the wire slowly loosens up and eventually falls out.

One of the most common wiring issues is that the C wire isn’t installed.

This common wire powers the Nest.

It’s not always an essential part of your thermostat, but it may cause issues like the one you have.

To fix this, shut off the HVAC and Nest power in the breaker box.

Remove the Nest from the wall and carefully inspect the wires.

If you see a loose wire, remove it completely and put it back into the terminal.

Pay special attention to the C terminal. If the common wire is missing, identify it and install it.

4. Check and Repair Your AC

If the thermostat isn’t cooling down your home, there’s a chance it’s the AC’s fault.

Most people don’t realize that an AC needs a lot of maintenance to function correctly.

It needs new air filters monthly, and the fins and the fan shouldn’t be caked with dust either.

Additionally, your AC needs enough coolant to work.

Of course, all these issues with your AC are noticeable in the daytime as well.

So, clean all components of your AC and check if you need to refill the coolant.

5. Check Your AC Drain Pan and Drain Lines

Your AC drain pan will fill with water from condensation over time.

The drain lines can get clogged with leaves and dirt, so you will need to flush them.

When the drain pan and drain lines get filled and clogged, your AC won’t cool properly.

The problem may worsen at night because the temperature drops cause the trapped water to expand or freeze.

The fan will still work, which might make you think that the issue is the Nest thermostat’s fault.

Here is how to clean your AC’s drainage system:

1. Remove the cap from the drainpipe.
2. Brush the drainpipe with a thin wire brush.
3. Mix equal parts bleach and water and pour it in. You can use vinegar in place of bleach too.
4. Let the mixture sit for 15 minutes and turn the AC on.
5. If the drain pan is still full, wait for another 15 minutes and turn the AC on.

6. Replace the Battery on an Older Nest Model.

If your Nest thermostat has kept you happy and cool for years until recently, it could be a bad battery.

This is also related to the common wire issue I explained earlier.

The C wire powers the Nest thermostat.

If it doesn’t supply enough power, you won’t have enough juice in the battery, and the thermostat won’t work.

This is a surprisingly common issue.

That said, you don’t have to replace your old Nest with a newer one.

In most cases, replacing the battery will get your AC back up and running at night again.

Cameron Sino explains in this video how to replace the battery in an older Nest thermostat:

7. Have Your Utility Company Remove the Electricity-Saving Box

Rochelle Ann G. explained that utility companies install electricity-saving boxes in HVAC systems to control how much power you’re using.

If your AC works fine during the day but not at night, this could be the issue. 

Electricity is cheaper at nighttime, so people turn on power-consuming appliances then.

At the same time, the energy-saving box will cut out power flowing to your HVAC if it detects high power consumption.

You can find the box near the AC or breaker box. It usually has a couple of red and green flashing LEDs.

If you have this box, find a technician who can safely remove the box.

You can call the company that installed your HVAC system and have them do it for you.