At SmartHomePerfected we pride ourselves on providing trustworthy, unbiased information. If you buy through links on our site, we may earn a small affiliate commission at no extra cost to you. Learn more

Thermostats are sometimes prone to problems non-technical users can find hard to figure out. Honeywell is one of the most popular thermostat manufacturers and most of the problems that arise in it are identifiable. If your Honeywell thermostat is not working, this guide will help figure out what is wrong, and how to fix it!

What kind of thermostat do you have?

To figure out what’s wrong with your thermostat, you first need to determine the type of thermostat you have. Manual, programmable, or smart?

Manual thermostats

The manual thermostat is the traditional dial-shaped thermostat. With no digital display, it won’t be able to show error codes making it harder to figure out what’s going on in case of a malfunction.  

Programmable thermostats

The programmable thermostat comes with a digital display and lets you set temperature programs according to your schedule. Such a thermostat can usually be programmed for the entire week, with older versions having 2-3 day programs.

Smart thermostats

Intelligent and intuitive, the smart thermostat is the most technologically advanced model on the market. It learns to program itself based on your schedule and comes with many advantages such as lower energy bills, remote access, and many more.

For problems that are specific to the model you have, you can fetch the manual below. However, before that, go through the guide to see if the problem is one of the common ones. Go to this page to read the Honeywell thermostat instruction manuals.

At SmartHomePerfected we always advise readers not to undertake any work they are not competent in performing and if in any doubt, it is best to seek the assistance of a professional.

Is the thermostat display on?

If your Honeywell thermostat is not working and there is no display, we recommend you work through the following troubleshooting steps.

1. Check the power

The first step will be to see if your thermostat is powered properly. If the display of your thermostat is not on or is fading, your device might be losing power or not getting power at all. Check the circuit breaker and the lights on your HVAC system. If you have a battery-powered thermostat, proceed to the next step.

2. Check the batteries

If your thermostat’s display is not responding, chances are the batteries have run out. Even in cases of screen flickering, fading, or completely turning off, replacing the batteries might quickly solve your issue.

If the batteries are too low, the thermostat won’t have a constant power supply and you might experience interruptions. Most thermostats have batteries and still take power from the HVAC system, but some models work only on batteries.

Check out our extensive guide here on how to replace batteries for all Honeywell thermostats models. 

3. Check furnace doors

If your thermostat is connected to a furnace, it is possible that the furnace door is not shut properly. Furnaces usually have a door switch and some thermostats are sensitive to this.

Check if doors are closed and sensors are working. Watch this video to learn how to open the furnace cover and check the door switch.

4. Check if the thermostat panel is pressed in

You might also want to check if the thermostat panel is firmly pressed in. Maybe you have recently replaced the batteries or other components of the thermostat and you left the panel partially open by mistake. If the panel is not pressed in perfectly, the display will not turn on.

5. Check the wiring

Wiring issues can prevent your thermostat from getting power. This problem can arise especially if you recently took the thermostat off the wall to replace its batteries.

Start by unscrewing the thermostat and check if all wires are connected correctly. Make sure no wires are loose. Verify if a wire is connected to the red-colored R terminal.

If your thermostat needs a C-wire, check to see if a wire is connected to the usually black-colored C terminal. To get a clear understanding of color codes in thermostat wiring, give this guide a read.

6. The thermostat might need replacing

If you already tried all the options above but your thermostat is still blank, you might have to consider replacing it. Go through the thermostat model-specific guide that Honeywell has provided to see if there is any specific issue you might have missed. You can also ask for help from a professional HVAC technician.

Cool on / Heat on message flickering

When Cool on / Heat on is blinking on your Honeywell thermostat screen, chances are your thermostat has been recently turned off or on. For instance, when batteries are replaced, the thermostat and the HVAC system need up to 5 minutes to start running again.

However, if the system doesn’t start shortly after, you may want to investigate further. Check out our guide here to troubleshoot this issue.

Honeywell thermostat says heat or cool but you're not feeling it?

If your Honeywell thermostat is not working despite saying it's currently heating or cooling then try out the following troubleshooting steps.

1. Check the mode and temperature

If the heating/cooling system does not respond to your Honeywell thermostat, there might be a problem with the selected mode. Check to see if the thermostat is in the correct mode – heat or cool.

Also, verify if the temperature is set lower or higher than the ambient temperature, depending on summer or winter respectively.

2. Check the temperature sensor

Sometimes the temperature sensor of your thermostat may be malfunctioning. You can manually check the temperature of your room with a normal thermometer and compare the results. Is the thermostat displaying the temperature accurately? If you observe differences, your temperature sensors need to be replaced.

3. Amp it up

Turn the heat or cold up to full by raising or lowering the temperature respectively. Wait a few minutes and see if the fan turns on. If the fan is not turning on, the problem is either with the wiring of the thermostat or the device is defective and needs replacing.

4. Check the wiring

Underlying wiring issues can prevent your thermostat from working properly. We recommend you unscrew the thermostat and check if the wires are connected correctly. 

Take it out of the wall and carefully examine if all wires are attached properly. Make sure none of them are left loose or disconnected.

For cooling, check if Y and Y2 are attached to the correct color wire. For heating, check if W and W2 are attached to the correct color wire. Also, you may want to verify if there are Rh and Rc wires in your system and whether they are attached to the proper terminals identified by the correct color.

To learn more about thermostat wiring color codes, give this guide a read.

5. Check individual components

Another option is to check all individual components of your HVAC system. There might be a problem with the furnace/boiler or the heat pump. Likewise, for the air conditioning system, the indoor or outdoor fan may be out of order.

Carefully check if all components of your HVAC system are on and see if they are not showing any error lights that may signal a malfunction.

6. Call a technician

Have you already tried all possible options but are still having trouble with getting your Honeywell thermostat up and running? If none of this works, then it might be time to call an HVAC technician to address the situation.

Honeywell thermostat not working – Conclusion

We hope you find the possible solutions and remedies presented above useful in determining and solving your HVAC issues.

If you are facing difficulties, don’t forget you can always seek professional assistance from an HVAC technician, especially if your problem persists and you can’t fix it on your own. Also, feel free to leave us a comment in the section below and we will shortly get back to you with answers!



Show CommentsClose Comments


  • Harry Frykas
    Posted December 7, 2022 at 6:01 pm

    recently perches a Honeywell home thermostat T4 Pro. had it installed by a heating plumbing company. we haven’t totally programmed it yet but we have it set at a temperature of 19.5c .this thing decides to for no reason set itself to 16.5 or maybe 25. Sometimes we find the fan setting has changed itself to no instead of where we left it as auto. Not sure if this one is a smart thermostat? my thinking is that if it was sett on hold, nothing should change.

  • Jim
    Posted July 25, 2022 at 2:11 am

    We have a programmable Honeywell thermostat that we had installed with by a new system about 10 years ago. It has worked fine until I changed the batteries.

    The three in it were starting to corrode a little but cleaned the contacts carefully and replaced the batteries. When replacing the thermostat on the base, I made sure the male connectors were aligned and carefully pressed it into place. Immediately it lit up and worked fine. After a half an hour it the display went out again. About an hour it relit. It has been working that way for about a week.

    Any ideas??

  • Barbara Thomas
    Posted May 13, 2022 at 4:53 pm

    Its been less that a tear since I bought this Honeywell Home Thermostat. Yes I have tried everything. starting with the battery. In frustration I have set all the setting to 70 degrees. Again I have woke up to 62 degrees. The furnace will kick in later today. maybe.

    I’d like this problem solved or replaced. It’s been moths of try this try that. I’m f’n freezing.

Leave a comment