When your Honeywell thermostat suddenly stops turning on the heat, your home can within hours become uncomfortably cold. When a malfunction like this occurs, you usually want to rectify it as soon as possible. Many times, however, you discover the problem after working hours, and you don’t want to call out your HAVC professional at night. You then wonder whether you will be able to troubleshoot the issue yourself and, if you’ve found the problem, be able to fix it.  

Honeywell thermostat not turning on heat could be due to faulty wiring, bad temperature settings, or bad batteries. Solving this is as simple as changing a heat setting, turning on a tripped circuit breaker, or replacing the thermostat’s batteries.

honeywell thermostat

In this article, I’ll explain to you my unique “categories of actions” troubleshooting method and show you how to implement it to fix the problem with your thermostat which won’t turn on the heat

My troubleshooting method

When you are troubleshooting, a specific sequence of steps is not necessarily needed. The troubleshooting “steps” are often only the different aspects to check and repair when needed. But sometimes you don’t know in what sequence you have to execute the steps. 

Therefore I’ve developed the “Category-System” to assist DIY-ers in saving time when troubleshooting. The aspects you have to troubleshoot are grouped into categories so that you can attend to the aspects which are not so time-consuming first.  

In this article, I’ll take you through the categories to help you find and fix the problem with your thermostat, which is not turning on the heat.  

The troubleshooting grid

CategoryType of issueDescriptionAspects to check
1Setting IssuesChecking all relevant settings without removing the thermostat from the back plate or wall.The thermostat’s temperature setting, The temperature offset setting, and The thermostat mode.
2“External”  issues 
Aspects you can check without opening the thermostat or taking it off the wall.The thermostat’s circuit breaker, Your furnace, Your thermostat’s (older models) level position, and Temperature sensor.
3“Internal” issuesAspects where you’ll have to open the thermostat and/or remove it from the wall.The thermostat’s batteries, The thermostat wiring, and The thermostat’s location4Resetting Resetting your thermostat.Resetting.

Category 1: Troubleshooting temperature setting issues

The thermostat’s temperature setting might be too low

You could have accidentally set your thermostat’s temperature lower than the usual ambient temperature in your home. If it is set too low and your home’s ambient temperature is never below the set temperature, the heat will not be turned on. For example, if the thermostat is set on 70 degrees, it will only turn on the heat when your home’s ambient temperature becomes below 70 degrees. If the ambient temperature is never so low, your thermostat will never turn on the heat. 

So, check the temperature setting on your thermostat and if it is too low, set it to the temperature level you prefer your home to be. Your thermostat should turn on the heat within a few minutes.

If the temperature setting has not been the problem or if you’ve altered the temperature and the heat is still not turning on, check whether the thermostat’s offset has been set, and if so, whether the differentiation is not too much. 

The thermostat’s temperature offset might be set incorrectly

Remember, your thermostat won’t turn on the heat if it “thinks” that your home is warmer than the set temperature. This might happen if the temperature offset is set too high. A temperature offset might have been set on your thermostat by your HVAC technician during the installment of the thermostat. 

A temperature offset is usually used when the thermostat is installed at a place where it is difficult to measure the home’s temperature accurately, for instance, behind thick curtains. The temperature measured by the thermostat behind the curtains might constantly be different to the home’s actual ambient temperature. To compensate for this, a temperature offset can be set. 

But a temperature offset should not be more than one degree either way.  If it is more, say, for example, 3 degrees, the thermostat will display a current temperature reading that is three degrees warmer than what the environment actually is. Thus it will not ask for heat. 

To solve the problem, you have two choices. You can set the temperature offset to only one degree, or you can just set the thermostat’s temperature higher. 

Your thermostat is not set to heating mode

Your thermostat’s mode might not be set. Usually, on modern thermostats, your thermostat screen will give you the option to set the thermostat on “Heat-mode,” “Cool-mode,” or “Off.” Ensure that it is not set on “Off” and that “Heat-mode” is activated.

If the Category 1 troubleshooting aspects haven’t solved your problem, you have to proceed to Category 2. 

Category 2: Troubleshooting External Issues

Check whether the thermostat’s circuit breaker is on

When the thermostat is not receiving any power, it can’t regulate the temperature and thus, does not ask for heat. The most common reason why the thermostat is not receiving power is that the circuit breaker has tripped. 

There are many reasons why a circuit breaker trips but these reasons are not relevant if the thermostat’s tripped circuit breaker doesn’t trip again when you turn it on. A surge in the electrical power could have caused the breaker to trip, and when it is turned on again, it will stay on. 

Remember, to turn a tripped circuit breaker on, you first have to press the switch down completely and then press it up until you hear a click sound. Then you know the circuit breaker is on again.

If the circuit breaker has been tripped and stays on after being turned on again, wait a few minutes and your heat should turn on. (If the breaker keeps on tripping, you have to troubleshoot that separately.)

Your furnace might be turned off

Usually, your Honeywell thermostat draws heat from your furnace. Thus, the furnace has to be on before your thermostat can call for heat and pump hot air into your home.

Check whether your furnace’s circuit breaker is on and if it is not, follow the same procedure described above for turning the thermostat’s circuit breaker on. (Sometimes, the furnace doesn’t have a separate circuit breaker but shares a breaker with all the HVAC devices.) 

If the circuit breaker is not the problem, check whether the On/Off switch on the furnace is on. Also, ensure that the furnace door is closed. 

Some furnaces have warning lights on them. When there’s an error, the light will flash or blink and show an error code inside the furnace cover. If an error code is displayed, refer to your manual to determine how to solve the problem.

When the furnace is on again, your problem might be solved.

Your thermostat (older models) might not be level anymore

If your thermostat is still an old mercury and bi-metal model, poor leveling of the thermostat can affect how well it responds to temperature changes in your home. Somebody could have bumped into the thermostat and moved it, or it could have been shifted during a cleaning session. 

Many older models relied on a bi-metal spring to sense temperature. A mercury switch is then affixed to the outside end of the coiled spring. As your home’s temperature rises and falls, the spring changes size. This tips the mercury switch on or off to bring your home’s temperature nearer to the thermostat’s set temperature.

To work effectively, the thermostat has to be absolutely level. If tilted, the heating system might never turn on. You can use a mini spirit level to determine whether it is still level or not. Usually, there are screws that you can adjust to get it level again. If you can’t get it level again, it is recommended that you replace it with an all-electronic model that has no moving parts. 

You might have to replace the temperature sensor

Your Honeywell thermostat’s temperature sensor assesses the temperature in your home. Depending on the information received from the sensor, the thermostat activates the cooling or heating system in your home. 

A faulty sensor might misread the room temperature and this may result in your thermostat not calling for heat. 

You’ll know the sensor is faulty when you use a thermometer to measure the temperature of your home and the reading doesn’t match the temperature displayed on the thermostat. 

To fix the problem, buy a new temperature sensor. 

Category 3: Troubleshooting Internal Issues

Your Honeywell thermostat might need new batteries (If Battery-Powered)

If your Honeywell thermostat model needs batteries to function, weak batteries might be the reason that the thermostat doesn’t perform all its functions such as calling for heat. 

To fix this, replace the batteries in your thermostat. The replacement batteries are alkaline AA or AAA batteries. To replace you have to 

  • turn off the Honeywell thermostat’s circuit breaker, 
  • pull your thermostat’s faceplate from the back plate to get to the battery holder, 
  • remove the battery holder from the base plate,
  • remove the old batteries and insert the new ones, 
  • place the battery holder back on the mounting plate,
  • push your thermostat’s faceplate back and switch on your Honeywell thermostat at the circuit breaker. 

If weak batteries have been the problem, your thermostat will now be able to turn on the heat again when needed.

Loose or incorrect wiring can prohibit your thermostat from turning on the heat

After you’ve made sure that no power is coming to the thermostat by turning off the relevant circuit breaker, take the thermostat off the baseplate and inspect the wiring. You can slightly pull on the wires to determine whether they are still secure. Check that the wires are inserted into the correct terminals. Usually, each wire in the thermostat will be labeled with some letters, and the terminals inside the thermostat will have the same letters. Ensure that each wire is in the thermostat’s receptor with the corresponding letter. 

If your thermostat is still not turning on the heat, you have to keep on troubleshooting. 

The location of your thermostat might be the reason why it is not turning on the heat

If your thermostat is installed near a window or open door, the outside temperature can affect your thermostat’s temperature readings.  The wind blowing on the thermostat from outside through the window or door can cause your thermostat to “feel” the wrong temperature and not call for heat. 

Move your thermostat to a place where open windows or doors won’t influence the thermostat’s temperature readings. 

Category 4: Troubleshooting Resetting

Resetting your Honeywell thermostat 

If none of your troubleshooting efforts has been successful and your thermostat still doesn’t turn on the heat, you’ll have to reset your thermostat. The different Honeywell models have different resetting procedures. 

The Honeywell thermostats 1000, 2000 and 7000 series

The Honeywell 1000, 2000, and 7000 series thermostats have the same resetting procedure:

After you’ve turned the thermostat and the circuit breaker off, remove the thermostat cover and remove the batteries – even if they are new ones. Then insert them in the opposite direction. In other words, place the positive end of the battery on the negative side of the battery holder on the thermostat. 

Wait for about 10 seconds, and then take the batteries out again. Re-insert the batteries correctly into the battery holder.

When you now turn on the thermostat and the circuit breaker, your thermostat has been reset.

The Honeywell thermostats 4000 series

The 4000 series comes with a reset button. To reset, turn on the thermostat and press the “Program” button thrice. Then find the reset button located inside a small hole on the front panel of the thermostat and use a sharp object to press the button for about 5 seconds. Now your thermostat has been reset.

The Honeywell thermostats 6000, 7000, 8000 and 9000 series

This series offers advanced features such as an onboard console and buttons and touchscreens. You reset the thermostat by using these features. Unfortunately, the resetting steps differ from model to model and you’ll have to find the correct way to reset your thermostat in its manual. 

Conclusion

When your Honeywell thermostat doesn’t turn on the heat, it can be very uncomfortable. Fortunately, it is one of the issues which you can troubleshoot relatively easy. 

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