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 heat.

These include, furnace 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

So, if your Honeywell thermostat won’t turn on heat, don’t worry, read on to learn how to have this problem sorted out.

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, lets dive right into why your thermostat heat is not working.

1. Your Furnace Not Turned On

When you have heating issues with your thermostat, the first thing that you want to rule out is 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 over 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 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 properly closed.

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 having checked the door and everything looks cool then 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 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 colours are not standardized so, you might want to check out what terminal each wire connects to on designation of the control board of your furnace. Incomplete thermostat wiring could cause a Honeywell thermostat flashing heat on but no heat 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 thermostat is set to heat. You can know for sure that your thermoset is on 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 need to change the mode to ‘heat’. 

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

However, it is worth noting that if you are unable to change the mode on your thermostat, you might have missed something when configuring your thermostat. In this case you’ll need to go to your installer guide and check the instructions on how to properly configure 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 the display, it can mean one or two things

  • Your thermostat is in delay mode: protecting your compressor and other equipment components from damage. Typically, when in delay mode, you will have a Honeywell thermostat flashing heat on but no heat coming through.
  • If 5 minutes passes 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 having tried tip 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 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 having reset your thermostat and the problem doesn’t go away, lets 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 it is only cold air coming it could be a sign that heat it not working.
  • If it is lukewarm air that is coming through vents when your thermostat is set to cooling, 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 properly or is misconfigured, it could be the reason your Honeywell thermostat won’t turn on 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, then 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 need to have the G-terminal connected 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 not uncommon to deal with Honeywell thermostat heat not working on auto. But it can become frustrating if you have this problem at a time when you need to keep yourself and your family cozy. We have tried out best to give the commonest 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 professional service to come and do the job. We hope this guide has been helpful.


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