Honeywell Thermostat Troubleshooting

Honeywell Thermostat Troubleshooting: Every Thing You Need To Know

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Honeywell is the manufacturer of a number of products for heat pumps, air conditioning, and residential heating systems. Irrespective of whatever HVAC system you are using in your home, or whether you are planning to buy a thermostat, some problems can occur and we can help you with solutions.

You can find Honeywell thermostats in different forms, including rectangular or round dial types that let you set a single temperature and an air conditioner that regulates the furnace to attain temperature near the selected setting. 

These devices are simply mechanical and their mode of function has nothing special. Most thermostats normally work using a simple vial of mercury along with a heat-sensitive bi-metal coil that either contracts or expands depending on the temperatures in the room

Nevertheless, most thermostats don’t use high-tech sophistication. And despite the fact that they are dependable and convenient, some are very old and have been functional for decades since their introduction in 1953.

However, Modern Honeywell thermostats are highly sophisticated digital electronic devices that are capable of automating the HVAC system to regulate temperatures inside your house using up to four different settings for each of the seven days of the week. In other words, you can set these advanced thermostats to automatically adjust up to 28 different settings in the course of one week. 

There are simpler models that only come with two levels of programming – one for weekdays and another one for the weekend. 

Although these remarkable analog and electronic thermostats from Honeywell are quite reliable, they can occasionally develop some problems. Read How to Set Honeywell Thermostat?

Thermostat Troubleshooting

Analog Thermostats Troubleshooting

You can find analog thermostats that are round or square in shape depending on the model. These thermostats normally come with a HEAT_COOL or OFF controls and an AUTO or OFF switch position that controls the fan.

Here are the steps you should follow to troubleshoot analog thermostats:

  1. To check whether the heater is operational, turn the thermostat to the HEAT position and set the temperature as high as possible. For instance, you can set the temperature to 80 degrees Fahrenheit and allow the furnace to activate in about 5 minutes. If you feel or hear the furnace activating, simply know that it is working well.
  2. Adjust the switch at the top of the thermostat to COOL and switch the fan to AUTO. You can either turn the dial or set the temperature switch to the lowest setting. For instance, set it at 60 degrees Fahrenheit. Give the thermostat about 5 minutes to find out if cool air starts to flow. If the AC unit kicks in, then your thermostat is functioning well.
  3. However, if nothing works after trying the above tests, then there is a problem with the heater or the air conditioner. You can remove the top cover and check if the small colored wires are well connected inside the unit with the help of a color-coded wiring diagram found in the user manual. In most cases, it is just a matter of restoring the low-voltage wire connections to get your thermostat working in the right way.
  4. What about if the wiring is ok? That indicates there might be a problem with the furnace if not the air conditioner. It may also mean that your thermostat needs replacement if it is very old. It will now be the right time to install a newer electronic programmable thermostat.

Digital Programmable Thermostat Troubleshooting

You can find digital programmable thermostats in different types and model numbers. Some come with keypads that have digital displays while others have touch screens. The most expensive and recent ones allow you to control your thermostat using your computer, tablet or smartphone. 

Below are examples of the most common issues that your digital programmable thermostat may experience and how you can restore its functions. 

Nothing Displays

Lack of anything to display is one of the most common problems experienced with digital programmable thermostats. Most experience this problem because:

  • The access door on the furnace is open or not completely shut. A good number of modern furnaces come with a door switch that only engages when the door is closed properly. The entire system cannot activate when the door is open or not fully shut. Failure to close the furnace door properly cuts power to the thermostat.
  • The batteries in the thermostat are completely discharged. If your thermostat uses batteries, replace them as that can cause display problems. A good number of digital programmable thermostats come with a battery alert that will prompt you to replace the batteries through a warning message on the screen.
  • The circuit breaker on the air conditioner or the furnace has tripped. Most building codes have dedicated circuits for furnaces and air conditioners, whereby the circuit breakers to these devices trip if there is a short circuit. Even if the circuit breaker has not tripped, switch it off and then on.

Thermostat Not Working Correctly

If your thermostat display is ok but the thermostat is not working as it should in regulating temperatures, examine if the following are the causes:

    • Disconnected low-voltage wires. Inside the thermostat, there are small colored wires that run from the main circuit to other components of the system. These wires should be connected properly for the thermostat to work as it should. Some thermostats only require three wire hookups although some require up to six or more depending on the number of components that come with your system. You can refer to the color chart that comes with your instruction manual in case you want to fix disconnected wires. 
    • Incorrect time of the day or the day of the week. The internal clock can lose its setting, particularly after power outages. Although the internal battery should hold the clock setting if there is a power outage, they don’t always work correctly. Check if the clock is set to the right time of day and week. You can follow the instructions on the user manual to set the correct time depending on your thermostat model number normally found at the back of the thermostat. 
  • Incorrect jumper settings. You can remove the top cover to check out if the jumper settings on your thermostat are correct. With some Howell thermostat models, you should ensure that the jumpers are in the right position depending on the air conditioner, the heat pump, or the furnace that you have. For instance, some Honeywell thermostats require the jumper in the HE setting for the electric furnace and the HG setting for your oil or gas furnace. This allows your fan to activate when switched to the automatic mode. Learn about “Nest Thermostat E Wiring Diagram

The Furnace or Air Conditioner Not Working 

Chances are that the problem has nothing to do with the thermostat but rather with your furnace, air conditioner, or another component. The problem can be anything to do with the humidifier or air-exchange unit. To find out where the problem lies:

  1. Set your thermostat in the COOL mode using the SYSTEM button, and lower the temperature to the minimum, and the fan set to AUTO. Give it 5 minutes to check if the unit will activate.
  2. Repeat the same steps for heat, with the fan set to AUTO. Switch on the system button until HEAT shows on the screen, and set the temperatures to the maximum setting. Wait for five minutes and find out if the heating unit will activate.
  3. If the two actions above don’t activate the furnace, air conditioner, or heat pump, then there is a problem in the thermostat and most likely it is in another component of the HVAC system. This is more likely if your thermostat is newly installed and you have already confirmed that the wiring is correct.

What Else Can You Check if  Your Thermostat is Not Working?

If there is no problem with the furnace, air conditioner, and heat pump, there are some areas that still require to be examined. 

Check for dirt and dust

Dust and dirt can bring to a halt the proper functioning of your thermostat. You can remove the cover of your thermostat and wipe off dirt and dust from wires and other components. This can be best done with the help of a dust sprayer and caution should be observed to avert further damages.

If you can’t access a dust sprayer, a soft brush with an attachment can be used gently and carefully to remove dirt and dust. There are some thermostats that come with two parallel metal strips. You can wipe off dirt and dust from the strips using a soft cloth.

Corroded or lose wires

Replace all the corroded wires and tighten up the lose ones. Find out if your thermostat will start working again.

The positioning of your thermostat

The thermostat functions by detecting the temperatures of your room and then compares it with the desired setting. If your room is too hot too cold, the thermostat will request for air or heat based on the temperature it detects. 

It is thus a good idea to place your thermostat in an area with a neutral temperature. This means that the environment should not affect the surrounding temperature. For instance, placing it in your kitchen is a bad idea because cooking can make the thermostat detect high temperatures emanating from cooking fumes. Place your thermostat in a well-insulated area.

Ensure your thermostat is leveled

Ensure that your thermostat is not slanted or tilted. Although this may irrelevant, it’s worth noting that your thermostat will only function properly if it sits in a leveled position. Mount your thermostat at least 5 feet from the ground.

Modify heat adjustments

Set your thermostat up to five degrees warmer during the heating season and up to five degrees during the cooling season. You should then find out the effect that these adjustments bring on your home.

NOTE: You should never open the top cover of your thermostat before unplugging from the power source. It is also advisable to plug it back to the power source after you have returned the top cover. 

Dealing with Extreme Temperature Changes

If you notice problems with extreme swings in room temperature while working with a gas- or oil-burning furnace, you may need a simple adjustment on your thermostat. Here are the steps to follow:

Remove the top cover

If you are using a mechanical thermostat with a mercury switch, use a small torpedo level to ensure that the thermostat is mounted level on the wall. It cannot measure the temperatures if it isn’t level.

Set the heat anticipator 

Most thermostats come with a small lever that moves along a calibrated scale which can be marked “longer”. This represents the heat anticipator.  It should be set one calibration mark closer to the “longer” setting if your furnace keeps going on and off frequently. 

Wait for a couple of hours for your thermostat to stabilize 

You can repeat these adjustments if your thermostat fails to stabilize. Consider replacing your thermostat if these adjustments don’t solve your problem. 


If you notice that your Honeywell thermostat is acting in a funny way, it is not working well, nothing is displaying on the screen, or there is poor communication to your cooling and heating system, there might be a problem. There could be issues with your thermostat or there may be mechanical problems with your ventilation, heating, or cooling unit.

Some issues that may prevent issues with temperature regulation inside your house may more likely be a problem with your heat pump, ventilation, A/C, or furnace. 

If your thermostat fails to respond after trying all the above troubleshooting ideas, consider replacing it with a more advanced model. Honeywell thermostat manufacturers have invested their energy and resources to ensure that they are in the frontline with a variety of products that will suit your home’s needs.

It is our hope that we have covered common issues that you might experience with your Honeywell thermostat. You can reach out to the manufacturer for a better walkthrough of your home’s heating settings if your problems are not resolved.



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