If your fan limit switch is set to AUTO but the fan continues to run without ever stopping, you’ll need to call a professional. Two problems that could cause your fan to run without stopping include: A bad fan limit switch that needs to be replaced. Bad thermostat wiring.

Why does my blower fan keep running?

Faulty Thermostat: If both the fan and either the cooling or heating system are running unexpectedly, you may have a faulty thermostat. Broken Relay Switch or Short Circuit: If only the fan is running, there may be a broken relay switch preventing the settings you enter on the thermostat from being sent to the fan.

Why is my fan running when my thermostat is off?

If the fan is the only thing running when the AC unit isn’t, there may be a faulty relay switch prohibiting the settings on the thermostat from being communicated to the fan. Another cause could be a wiring issue or a short circuit preventing the system from recognizing the on and off signals.

Why is furnace fan running non stop?

The fan limit switch is on the wrong mode

Now, if the furnace fan won’t stop running, it may be that either your limit switch has been set to manual override, or the switch itself is faulty and needs to be replaced. Your fan limit switch can be found right under the furnace hood.

What to do if fan keeps running?

Quote from the video:
Quote from Youtube video: Running some of the common causes are loose open or burnt wires inspect the wires. And connection condition.

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

Quote from the video:
Quote from Youtube video: Off if you turn the power off and then you turn it back on and the blower motor stops running but then you go to use the blower motor such as for heat for air-conditioning or for fan.

Why is my heater not turning off?

If your heater won’t turn off, the first thing you do is check the thermostat. The thermostat controls how the heating system runs. It detects the indoor temperature and signals the furnace to start or stop. So, if the thermostat malfunctions, it can signal the unit to run continuously.

Should furnace fan run constantly?

As previously mentioned, newer models of furnace systems include fans that are designed to run continuously. Assuming that your heating equipment was properly installed by a professional and has correctly-sized ductwork, letting the fan run continuously may actually help extend its service life.

How do I know if my fan relay is bad?

Keep a lookout for the following bad cooling fan relay symptoms:

  1. The engine runs hot or overheats. …
  2. The cooling fans don’t work. …
  3. The cooling fans keep running. …
  4. Warning lights. …
  5. Poor air conditioning performance. …
  6. Swapping Relays. …
  7. Measuring the Relay Coil’s Resistance. …
  8. Listening for Noises.

How long should fan run after furnace shuts off?

Typically, because the oil or gas burner is NOT running (because the thermostat is not calling for heat), the blower fan should not run more than a minute or two before stopping.

Where is the furnace fan limit switch located?

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Quote from Youtube video: And what temperature settings to adjust each of these three pins to so the fan limit control is located typically. Right behind the electrical gas valve. And it's located in the heat exchanger area.

What does a furnace limit switch look like?

Quote from the video:
Quote from Youtube video: The limit switch monitors the temperature of the air passing over the heat exchanger.

How much does it cost to replace a limit switch on a furnace?

The cost to replace a limit switch on a furnace is $100 to $375 on average. The fan-limit switch has sensors that shut off the blower motor when it overheats.