Honeywell Thermostat Not Cooling [8 Easy Solutions]

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Is your Honeywell thermostat not cooling? This can be very frustrating especially if you woke up to a hot night. There are a few reasons your Honeywell thermostat is not cooling, and these include:

  • Thermostat not set to cool mode
  • Furnace door not closed
  • Tripped Circuit breakers
  • Issues with thermostat wiring
  • Thermostat not correctly configured
  • Malfunctioning reverse valve
  • Low thermostat batteries
  • Issues with your HVAC system
Honeywell thermostat not cooling
A man setting thermostat to cooling

Read also: Honeywell Thermostat Blank Screen [7 Fixes]

8 Reasons for Your Honeywell Thermostat Not Cooling

1) Thermostat Not Set to Cool Mode

When your Honeywell thermostat is not cooling, the first thing you want to do is verify your thermostat settings. Make sure that your thermostat is in cool mode. Your display should indicate a snowflake icon or a ‘cool on’ message.

If the ‘cool on’ message and the snowflake icon are flashing, that could mean that your thermostat is in delay mode. A thermostat can go in delay mode to protect your cooling system from. This can last up to 5 minutes.

To know for sure if your thermostat is cooling, adjust the temperature to a point below your current room temperature. In fact, you can quickly know if cool is working by lowering temperature on your thermostat to the lowest point.

If you notice cool air flowing in after a few minutes, that’s a sign that cooling is working, and you can now set the temperature to a point you want.

2) Furnace Door Not Closed

When a thermostat goes into delay, this should not take more than 5 minutes.  If it’s taking longer than 5 minutes, there is definitely something else going on. This is what you can do to resolve the flashing cool message on display:

  • Check that the furnace door is securely closed.  Furnace doors do have switches that cut power to your HVAC system when they are open.
  • Make sure that the furnace power switch is on: If the power switch is off, you HVAC system can’t turn on. This could be the reason your Honeywell thermostat is not cooling

3) Furnace Circuit Breakers

 After having checked with the power switches and you don’t notice any ‘off’ switches, head over to check with the circuit breakers.  Usually, a heat pump will be installed with two circuit breakers, one for the indoor evaporator coil and another one for the condensers coil. Flip back the breaker switches if they are tripped.

4) Issues With Thermostat Wiring

Bad thermostat wiring could be the reason for your Honeywell thermostat not cooling. If you recently installed the thermostat and this is the first time you want to use it for cooling, consider going back to the drawing board and verify with your thermostat wiring.

You’ll need to make sure that:

  • The wiring was correctly matched from the old thermostat to the new thermostat.
  • R and R c terminals are connected by separate wires.
  • Alternatively, go through your Honeywell thermostat user manual for more guidance depending on your model.

5) Thermostat Not Correctly Configured

Apart from thermostat wiring, another issue that affects the cooling and heating functionality of your thermostat is the configuration. If your thermostat was not configured correctly, this can prevent it from going into the cooling mode or heating mode.

Go to the installation and user manuals for your system and thermostat and confirm that your thermostat is correctly configured for your type of cooling system and for all stages of your HVAC system.

Reconfiguring your thermostat correctly can resolve the issues. Otherwise let’s go to the next step.

6) Malfunctioning Reverse Valve

A reverse valve helps your heat pump to switch between heating and cooling mode.  However, when the reverse valve malfunctions, it can get stuck in one operating mode, that is heat mode or cool mode.

If your Honeywell thermostat is not cooling, try putting it in heat mode. If heat is working, then the problem could be with the reverse valve. Reverse valves are replaceable. You need to call a HVAC guy to come and have a look.

7) Low Thermostat Batteries

Low thermostat batteries can cause many issues to your HVAC system.  Some problems caused by a low battery include:

  • Heating and cooling system not responding to temperature adjustments on your thermostat
  • Difficulties powering on and off your system.

If you think you are dealing with a low battery issue, this is an easy fix that you can carry out yourself.  Swapping batteries should solve the problem. To change batteries in your thermostat, remove the thermostat from the wall. will have screws.

Usually, all Honeywell thermostats that use batteries will display a ‘LOW BAT’ message a couple of months before they die out.

Sometimes when your thermostat is not cooling, all it needs is a reset. You can reset your thermostat by pressing and holding the rest button a few seconds or by removing the batteries from your thermostat it and inserting in reverse for about 30 seconds.

Other Issues That Prevent Your AC from Cooling When Your Thermostat Is On Cool

Leaking Refrigerant

A leaking refrigerant will prevent your AC from cooling your home despite your thermostat been set to cool mode. The refrigerant is a chemical that is used in air conditioners as a medium to transfer heat between your indoor environment and outdoor environment.

As air flows around the evaporator coils, the refrigerant in liquid form will absorb heat from this air and turns into gas. Then the compressor pressurizes this gaseous refrigerant and sends it to the condenser coil.

In the condenser coil, the refrigerant releases heat as it condenses back to liquid. The cycle continues until the temperature indoors meets what you need.

Covered Condenser Unit

A condenser unit that is covered in debris, soil and other objects will have a hard time disposing heat from indoors. The outdoor condenser unit has a blower fan, condenser coils and a compressor.

The blower fan draws air into the unit so that this air can take away the heat when leaving. But when air flowing in and out the condenser unit is restricted, much of the heat will not be released.

And when dirt settles on the coils, it can make it even hard for heat pump to cool your home. However, a dirty outdoor unit can easily be cleaned by rinsing it with a hose.

Final Thought

When you are dealing with a Honeywell thermostat not cooling, try out the tips given in this guide. They could save you that call to HVAC professional services. However, if your AC will not cool after trying out our tips, it is in order to call in an HVAC technician to come and take a look at the problem.

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