Honeywell Thermostat Heat Not Working [7 Fixes]

Is your Honeywell thermostat heat not working on auto? There can be any number of reasons your Honeywell thermostat won’t turn on the heat.

The main causes why your Honeywell thermostat won’t turn on the heat would be from the furnace is not turned on, furnace door not properly closed, issues with thermostat wiring, reverse valve issue, incorrect thermostat settings, and others that we’ll be looking at shortly in this article.

Honeywell thermostat not heating
A man keeping warm

Reasons For Honeywell Thermostat Heat Not Working on Auto

When you are starting to troubleshoot any issues, you will start with the easiest to check and fix. So, let’s dive right into why your thermostat heat is not working.

1. Your Furnace Not Turned On

When you have heating issues with your thermostat, you first want to rule out the power supply to your thermostat. Is your thermostat turned on? Check the furnace switch if it’s turned on. A furnace switch is usually found close to your furnace and looks pretty much like a light switch.

If your furnace is turned on, head to your circuit breaker to check for any tripped switches. Sometimes, tripped circuit breakers could be the reason you have a Honeywell thermostat heat not working. If your furnace has a power supply but not heating when you turn on your thermostat, then go to the next step.

Read also: Furnace will not turn on with thermostat [Easy Solutions]

2. Furnace Door Not Closed Properly

You have now checked your furnace, and it’s powered up. At this point, you need to find out if the furnace door is closed correctly.

Some heating systems won’t just work if the cover is open or not properly closed. They have a door switch that cuts power to your furnace when it is partially closed or fully open.

Besides, be sure to check for any error codes on your furnace. If there are any errors, you will normally see rapid blink lights. You can find the error code reference inside the furnace door.

After checking the door and everything looks cool, let’s move on to the next step of troubleshooting.

3. Thermostat Wiring

If your Honeywell thermostat is set to heat mode, but no heat is coming but just lukewarm air, it’s possible that you have thermostat wiring issues. You will need to make sure that the wires are correctly connected. You can check the user manual for instructions about your thermostat wiring.

To check if your thermostat wiring is done right, gently pull the thermostat from the wall. Some thermostats can have screws or buttons.

It should be noted that wire colors are not standardized, so you might want to check out what terminal each wire connects to on the designation of the control board of your furnace. Incomplete thermostat wiring could cause a Honeywell thermostat to flash heat on, but no heat is coming.

4. Thermostat Settings Could Cause a Honeywell Thermostat Flashing Heat On But No Heat

One of the commonest issues that homeowners overlook is the thermostat setting. You need to make sure that the thermostat is set to heat. You can know for sure that your thermoset is on the heat if it has the following icons on display.

  • Sun or fire icons
  • “Heat on” or “heat message”

If your thermostat doesn’t show any of the above messages or icons, you must change the mode to ‘heat.’ 

And after changing the mode, you should set the temperature point higher than the current temperature and wait a few minutes to see if heat will start coming through.

However, it is worth noting that if you cannot change the mode on your thermostat, you might have missed something when configuring it. In this case, you’ll need to go to your installer guide and check the instructions for properly configuring your thermostat.

Assuming that you have now configured your thermostat properly, you should be able to see the heat message on display. But if the ‘heat on” message is flashing on thedisplay, it can mean one or two things:

  • Your thermostat is in delay mode: protecting your compressor and other equipment components from damage. Typically, you will have a Honeywell thermostat flashing heat on in delay mode, but no heat coming through.
  • If 5 minutes pass and the flashing message doesn’t go away, you might need to restart your thermostat. You can do so by flipping off the power switch for 5-10 minutes and flipping it back on. If this doesn’t help, you can go through the user manual guide for getting rid of the Honeywell thermostat flashing messages.

Also read: Furnace not blowing air through vents [5 Easy Solutions]

5. Reset Your Thermostat

thermostat blinking "cool on"

Another easy fix is resetting your thermostat. After trying tips 1-4 and nothing seems to be working, you can try resetting your thermostat. But before resetting it, make sure you take note of your important settings because they all get erased after resetting your thermostat.

This is how you reset your Honeywell thermostat:

  • Make sure your thermostat is powered on
  • Press the menu button for about 5 seconds
  • Find the reset option and click it
  •  Then select factory defaults and follow the instructions that follow

After resetting your thermostat and the problem doesn’t disappear, let’s go to the next step.

6. Furnace Blower

If you have tried every troubleshooting tip we have given so far, and nothing seems to be working, you still have another option to try out. You’ll need to find out if cooling is working, and this is how you do it:

  • Try switching your thermostat from heating to cooling and feel the air that blows out of your vents. Is there any air at all? If only cold air is coming, it could be a sign that heat is not working.
  • If it is lukewarm air that is coming through vents when your thermostat is set to cool, it’s a sign that the reverse valve maybe misconfigured or not wired properly.

7. Misconfigured Reverse Valve Could Be Why Your Honeywell Thermostat Won’t Turn on Heat

If the reverse valve is not wired correctly or is misconfigured, it could be the reason your Honeywell thermostat won’t turn on the heat.

To resolve the reverse valve issue, turn the fan mode on and go to the vent. If the heat is weak or not coming out at full force, we’ll need to go back to the wiring and verify that everything is in order. Do the following:

  • Gently remove the thermostat from the wall; if it has screws, remove them. Now check if there is a wire connected to the G-terminal. You must connect the G-terminal to a wire for the fan to run.
  • If the G-terminal is connected, but your fan isn’t working, there could be a problem with either a blower capacitor or a broken blower motor belt (for older furnaces.) In this case, you may want to call in a professional HVAC guy to come and take a look.

Read also: AC Heat Mode Not Working [5 Easy Fixes]

Final Thought

It is common to deal with Honeywell thermostat heat not working on auto. But it can become frustrating if you have this problem when you need to keep yourself and your family cozy. We have tried out best to give the most typical causes to that issue together with possible solutions.

But if you feel you cannot handle anything on your own, it’s smart to call in a professional service to come and do the job. We hope this guide has been helpful.


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