Honeywell Thermostat Not Cooling: How to Troubleshoot

If your Honeywell thermostat won’t turn on your AC and you’re not sure what to do, keep reading. In this post, we’ll explain why this is happening and how to troubleshoot the problem. Let’s get started.

Honeywell Thermostat Not Cooling

If your Honeywell thermostat isn’t cooling, here are some reasons this might be happening:

  • You haven’t set the thermostat to Cool mode.
  • Your thermostat is delaying its cooling settings.
  • Your Honeywell thermostat is not compatible with your HVAC system.
  • You didn’t connect your HVAC wires to your thermostat.
  • Your circuit breaker is turned off.
  • The batteries in your thermostat are low.
  • Your C-wire is damaged.
  • Your furnace is off or the furnace door is open.

That said, let’s look at how to get your Honeywell thermostat to work properly again.

Honeywell Thermostat Not Cooling: Try These Troubleshooting Steps

1. Set Your Thermostat to Cool Mode

Your Honeywell thermostat may not cool your room if you don’t set the device to Cool mode.

To activate cool mode on your thermostat, tap Mode on the device screen until the mode changes to Cool. Also, press the minus button on the left side of the screen to achieve your preferred temperature setting.

Note that the procedure for activating Cool mode on your Honeywell thermostat depends on the model you have. If you’re not sure how to set your Honeywell thermostat to Cool mode, refer to your user manual.

If your thermostat doesn’t cool your home after setting it to Cool mode, try the next tip.

2. Wait for Your Thermostat to Load Your Cooling Settings

Do you see “Waiting” or “Cool On” flashing on your Honeywell thermostat screen? If so, your thermostat might just be taking a while to cool.

Sometimes, the Honeywell thermostat enters delay mode when you set the device to Cool. This prevents your AC from short cycling.

When the thermostat goes into delay mode, it displays “Cool On” or “Waiting” on its screen. If you see those words on your thermostat, wait for about 5 minutes. Your Honeywell thermostat should start cooling by that time.

3. Check if Your HVAC is Compatible with Your Honeywell Thermostat

Did you just install your Honeywell thermostat? Then the device might not be cooling because it doesn’t support your HVAC system.

Most Honeywell thermostat models only work with low-voltage systems. So, if your HVAC unit is not a low-voltage system, your thermostat may not cool your home.

If your Honeywell thermostat is not cooling, check if your HVAC unit is a low-voltage system. Below are 4 signs that can help you determine if your HVAC system is low-voltage. Usually, a low-voltage system contains one or more of these features:

  • You have a boiler, heat pump, or central air conditioner in your home.
  • There is a furnace in your home.
  • If you connect one thermostat to your system, it will control the temperature in several rooms in the house.
  • The floors in your rooms contain heating vents.

If your HVAC system has none of the 4 features listed above, it might not be a low-voltage system. In that case, you’ll need to replace the Honeywell thermostat with an option that is compatible with your HVAC unit.

If you have confirmed that your HVAC unit is low-voltage, yet your thermostat isn’t cooling, move on to the next step.

4. Connect Your HVAC Wires to Your Thermostat

If your Honeywell thermostat isn’t cooling, you may not have connected your HVAC wires to the thermostat.

Your HVAC system provides cool air in your home. So, your thermostat needs to be connected to your HVAC to cool your room. The HVAC wires on your circuit board connect the HVAC unit to your thermostat.

If your thermostat isn’t cooling, check if you have connected your HVAC wires to the device. If you haven’t inserted the wires into the thermostat, do it now.

Follow these steps to connect your HVAC wires to your Honeywell thermostat:

  • Go to your circuit board and search for the terminals R (Power), Rc (Red Cooling) Y (AC), and G (Fan)
  • Open your Honeywell thermostat package. You’ll see labels titled R, Rc, Y, and G.
  • Put the R and Rc labels on the wire connected to the R and Rc terminals.
  • Also, attach the Y and G labels to their corresponding wires.
  • Now, unmount your thermostat. Then detach the R, Y, and G wires from your circuit board.
  • Insert these wires into matching terminals on the thermostat’s mounting plate.
  • Now, re-attach your thermostat to its stand.

Once you’ve connected the wires to your thermostat, the thermostat should start cooling. But if the device doesn’t cool your home, continue to the next step.

5. Flip On Your Circuit Breaker

If a temporary power outage occurs in your home, your thermostat may suddenly trip and go off. As a result, your thermostat will turn off.

Your Honeywell thermostat won’t cool if there is no power in the device.

If your thermostat isn’t cooling, check if the device is still turned on. If not, go to your circuit panel and flip the breaker to turn it on. Your thermostat should turn on now and start cooling.

However, if your Honeywell thermostat doesn’t cool after you’ve switched on the device, go to the next tip.

6. Change the Battery in Your Thermostat

Your Honeywell thermostat may not activate cool mode if its battery is low. This is because the thermostat automatically turns off most of its functions when it has a low battery.

If you don’t feel the cool air in your room after setting your thermostat to cool mode, check the device’s screen. You will see a Low Battery warning on the screen if the thermostat’s battery is low.

To fix this issue, you’ll need to change your thermostat batteries.

The following guide will show you how to change the battery in your Honeywell thermostat:

  • Switch off your thermostat.
  • Pull the device from its mounting plate.
  • Turn to the back of the thermostat. You’ll see the battery.
  • Remove the depleted battery from the battery compartment.
  • Now, insert the new batteries. Honeywell thermostats use AA or AAA batteries.
  • Place your thermostat back onto its mounting plate.
  • Now, turn on the thermostat. Your thermostat should activate cool mode in a few minutes.

If your thermostat doesn’t cool your room after you’ve changed the batteries, don’t lose hope yet. The following tips may solve the issue.

7. Replace Your C-Wire

Do you use a C-wire instead of batteries to power your Honeywell thermostat? Then the thermostat might not be cooling because your C-Wire is damaged.

If you notice that your thermostat isn’t cooling, detach the thermostat from its stand and inspect the C-wire. The C-wire is the wire connected to the C terminal on your thermostat.

If the C-wire seems bare or damaged, replace it with a new one.

Your Honeywell thermostat may still not cool your home after this. In that case, move on to the next step.

8. Switch On Your Furnace

Your AC works by converting hot air to cool air. This hot air is provided by your furnace. So, if your furnace is off, your AC won’t work. As a result, the thermostat won’t cool.

If your thermostat doesn’t cool your room, check if your furnace is turned on. If the furnace is off, switch it on.

Once you switch on your furnace, it will send hot air to your AC. The AC will receive the air and start working.

But if this doesn’t help, try the next tip.

9. Close Your Furnace Door

When you open your furnace door, a safety switch in the furnace pops and turns on. This switch turns off your AC and thermostat. Due to this issue, your Honeywell thermostat might not activate cool mode.

You can fix this problem by closing your furnace door. Your thermostat should start cooling now.

But if your thermostat doesn’t cool after you’ve closed the furnace door, continue to the final tip.

10. Ask an HVAC Expert to Inspect Your AC Compressor

The compressor transforms hot air to cool air in your air conditioner. That said, you won’t get cool air in your room if your AC compressor isn’t working properly.

If your thermostat doesn’t cool after you’ve tried all the tips above, contact your HVAC technician and ask them to inspect your AC compressor.

Your thermostat should start cooling once you get the compressor fixed.

Wrapping Up

If your Honeywell thermostat isn’t cooling, ensure that you’ve set the device to cool mode. Then wait for the cooling settings to load.

If these tips don’t work, check that your HVAC unit is compatible with your Honeywell thermostat. Also, ensure you’ve connected your HVAC wires properly to your thermostat.

Another tip you can try is flipping your circuit breaker off. Then flip it back on. Depending on your thermostat’s power source, you may also need to change the batteries or replace your C-wire.

If your thermostat doesn’t cool after this, check that you’ve switched on your furnace. Then close the furnace door.

If none of these tips work, you might have to ask an HVAC to inspect your AC compressor or contact Honeywell Customer Support for help.

You may also like to see how to troubleshoot blank screen issues in a Honeywell Thermostat and Lennox iComfort Thermostat.