Why is the fan always running on my Honeywell thermostat?

Author: Andres Schaden  |  Last update: Sunday, October 19, 2025

This is the normal setting for a system fan. The On position will turn the fan on to run continuously, regardless of whether the heating or cooling system is turned on by the thermostat or not. This is the setting used to move air in your application all the time instead of when the system is running.

Why is the fan continuously running on my Honeywell thermostat?

This is a common and normal condition of a working system if the fan switch is ON. With the fan running constantly, cool air will come out whenever the set temperature is reached, and will continue to come out until the heat turns on. When the system is heating again, the air will become warm.

Why is my Honeywell thermostat fan not turning off?

If your furnace fan won't turn off, you most likely have one of these 3 problems: Your furnace fan limit switch is set to “manual override” The fan limit switch is faulty and needs to be replaced. There's a problem in your thermostat wiring.

Why is my thermostat fan not shutting off?

if the fan continues to run after shutting thermostat completely off, possibilities include bad fan relay on thermostat, trouble shooting further, if control wiring is disconnected from thermostat( check for shorts) and fan continues to run, you have the contacts on the fan relay stuck together, and need a new relay.

Why is my fan always on my thermostat?

A faulty thermostat can cause your furnace fan to run constantly. Your thermostat should be checked for proper calibration, battery condition, and settings to ensure that it is working correctly. If you suspect an issue with the thermostat, try replacing the batteries or checking the wiring connections.

AC / Heater Blower Fan Stuck On - Troubleshooting and Repair

What causes a cooling fan to run constantly?

If the coolant level is too low, it can prevent the engine from maintaining an optimal operating temperature. This can trigger the fan to constantly activate in an attempt to cool the overheating engine. Topping up the coolant to the recommended level should rectify the problem.

Is it better to have your thermostat fan on auto or on?

Since the AUTO setting means the fan is only engaged when the system is on, rather than constantly blowing, AUTO is the most energy-efficient option between the two settings. This means you'll be using less energy and saving money on your electric bill by using the AUTO setting.

Why is my thermostat stuck on fan?

If the control board is faulty or malfunctions, it may not send the signal to the fan to tell it to shut off. The same can also happen if the wiring between the control board and the fan is damaged or there is a loose electrical connection.

What do you do if your fan won't turn off?

This isn't necessarily bad for your fan, but it is usually a sign of a bigger problem. Common causes for fans not turning off when they should include faulty thermostats, bad wiring, and stuck relays. These problems are not easy DIY repairs and should be left to an HVAC professional.

How do you reset a Honeywell thermostat?

Access the Menu: Tap the menu icon on the thermostat's touch screen. Hold Down the Weather Button: Press and hold the weather button for five seconds. This will bring up the reset menu. Select Reset Option: Navigate through the options until you find “Factory Reset.” Tap on it to select it.

Will a bad thermostat cause fan to stay on?

A bad thermostat can also cause the fan to run continuously or not turn off when it should. To ensure your thermostat is functioning correctly, it is recommended to consult with HVAC Alliance Expert's specialists.

What would cause a blower motor to continuously run?

Sounds as if you have a shorted wire. A lack of 24volts will cause the motor to run continuous in some units. An open high limit [as stated in a previous post] will cause the blower situation as well. Check for voltage across R and C at the furnace thermostat terminals, should have 24 volt.

How do I turn off my Honeywell fan?

If yours is like mine then you have two setting boxes. One if for “Heat”, “Off” and “Cool” and the other is for “Fan”. Set the fan box in the “Auto” setting and then the fan will only come on when heat or cool is called for.

What happens if a fan runs continuously?

Fans that are left on constantly can use more electricity than they should, and their blades will become dull quickly, even without being used. – Clean it regularly. The one major risk that you have when running an electric fan all day long is dust and debris building upon its surface.

Do Honeywell fans turn off by themselves?

Answer: The HYF260B Honeywell QuietSet Tower Fan features a timer setting that automatically shuts your fan off after 1, 2, 4 or 8 hours.

Should fan be on auto or on Honeywell home thermostat?

Keeping your fan on AUTO is the most energy-efficient option. The fan only runs when the system is on and not continuously. There is better dehumidification in your home during the summer months. When your fan is set to AUTO, moisture from cold cooling coils can drip and be drained outside.

Why won't the fan turn off on my Honeywell thermostat?

It was probably just that the electrical contacts in the relay or fan control are pitted and stuck together... it may or may not happen again. if you can find the little black fan relay box on the printed circuit board inside the furnace, you can try tapping on that with a hard object if it happens again..

Why is my fan running when my thermostat is off?

Your Furnace Fan Limit Switch Is Set to Manual

When the thermostat turns off—and no heat is necessary—the switch should turn off. However, if the switch is set to manual, the blower won't turn off. Check to see if your furnace's fan limit switch is set to manual.

What causes the fan to stay on?

The fan's job is to cool down the engine and prevent overheating, which can damage critical components. In many modern cars, the engine control unit (ECU) monitors the temperature, and if it detects that the engine is still too hot after shutting down, the fan will stay on until the temperature lowers to a safe level.

Should thermostat fan always be on?

Keeping your thermostat fan set to "ON" may seem like a great way to circulate air throughout your home or office, but it actually has some disadvantages. Using this setting does lead to more energy consumption, as the blower's motor runs more frequently - you may notice slightly higher energy bills.

Why does my Honeywell fan turn on by itself?

This is the normal setting for a system fan. The On position will turn the fan on to run continuously, regardless of whether the heating or cooling system is turned on by the thermostat or not. This is the setting used to move air in your application all the time instead of when the system is running.

What does it mean when the thermostat fan is on?

If you leave the “fan on” position. It will stay running regardless of heat or ac. This is done for air circulation. If smoke is in a room or something in the kitchen smells bad. You might turn it on.

Is it bad to leave thermostat fan on?

Leaving the fan running reduces wear and tear on the motor since it's not starting and stopping repeatedly. It's also beneficial to boost filtration, but leaving it on this setting has more drawbacks than benefits. When it runs nonstop, the fan consumes more energy, and the air filter needs frequent replacement.

Why not use AC and fan together?

Answer: You can— and should— run your A/C and ceiling fan together. Doing so can help lower your cooling costs each month, but only if you're using them right.

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