What tells the blower motor to turn on?

Author: Lina Lakin  |  Last update: Friday, December 26, 2025

The thermostat is what tells these separate systems to work together. In normal operation, when your thermostat is set to "auto," it will tell the blower fan plus the heating or cooling components to turn on and off at the same time when the desired temperature is reached.

What starts the blower motor?

When an HVAC unit is equipped with a PSC (Permanent Split Capacitor) blower fan, a capacitor is required to both start and run the motor. The capacitor's job is to store and then discharge electrical energy in order to create an artificial phase of electricity for the blower motor power supply.

What sends power to the blower motor?

In newer applications, the blower motor resistor is actually a solid state module that sends a varied signal to the blower motor. The traditional blower motor resistor is connected to ground and wired in series with the blower motor assembly. Blower motor resistors have several resistors with different resistances.

Why is my blower motor not turning on?

If your heater blower motor not working or heater fan motor not working, check for signs of wear and tear on the motor, belts, or bearings. Mechanical failures often result from years of operation without proper maintenance. A motor replacement or repair may be necessary to restore function.

What component proves the blower motor is running?

A sail switch would be used to prove that the combustion blower motor is operating before ignition. In this case, the sail switch will be used as a safety device. A sail switch is installed in the blower housing of an HVAC system's combustion blower assembly.

What tells the blower motor to turn on?

What controls the blower motor?

The blower motor resistor is responsible for controlling the blower motor speed.

How do I know if my blower motor is getting power?

You can test this by jumping out 120 volts to the blower motor wires; this will let you know if the blower motor works or not. 2. Ensure the capacitor attached to it is good – whether you do it before you jump out the blower motor or not, quickly check the capacitor to see if it meets manufacturer specs.

Can a bad fuse cause a blower motor not to work?

One of the most prevalent factors that can cause a blower motor to stop working is a blown fuse. A fuse prevents electrical circuits from an excessive flow of current that may run in them. Over time or due to any sudden surge, it might blow the fuse and cut power to the blower motor.

Why won't my HVAC blower kick on?

Common causes include electrical problems, a malfunctioning blower motor, or thermostat-related issues. Electrical problems may include blown fuses within the furnace circuit or tripped circuit breakers in your electrical panel. If the blower motor is worn out or has failed, it can cease to function altogether.

How do you diagnose a blower motor problem?

Look for these key indicators that you have a bad blower motor.
  1. Strange Rattling, Clanking, or Screeching. ...
  2. Weak or No Airflow From The Vents. ...
  3. A Sudden Spike in Your Energy Bills. ...
  4. An Overheating HVAC System. ...
  5. Replace or Maintain a Part in the Blower Motor. ...
  6. Replacing the Blower Motor. ...
  7. Keep Up With HVAC Maintenance.

What relay controls the blower motor?

It's controlled by the fan control switch and blower motor relay, which are responsible for managing the amount of voltage the blower motor receives, allowing it to function at different speeds.

Where does blower motor pull air from?

One of the hardest-working parts of your home's furnace is the blower motor. In a gas forced air furnace, it's located in a box at the base of the furnace next to the air filter, where it draws return air through the filter.

How do I know if my blower motor or relay is bad?

No Airflow: One of the most noticeable signs of a bad blower motor relay is the lack of airflow from the HVAC system. If the relay fails to activate the blower motor, it will lead to no air coming out of the vents, resulting in poor heating, cooling, or ventilation performance.

How to reset blower motor?

How Do I Reset the Blower?
  1. Turn off the circuit breaker powering your HVAC system.
  2. Unscrew the blower cover.
  3. Give the blower time to cool down completely before proceeding.
  4. Push the reset button (typically a red button behind the blower motor).

How do I know if I need to replace my blower motor?

You should replace your blower motor when you notice the following signs:
  1. Weak Airflow. The first indication that you have a faulty blower motor is when the airflow out of your air conditioner is weak. ...
  2. No Airflow. ...
  3. Unusually High Energy Bills. ...
  4. Strange Sounds. ...
  5. Overheating.

What controls the blower motor on the furnace?

The fan limit switch controls when the furnace blower fan turns on and off. This control also provides a safety limit that turns off the burner or furnace if temperatures at the furnace get too high. Fan/Limit switches are used on all types of heating furnaces.

Can a bad thermostat cause blower not to come on?

Thermostat Problems: An incorrectly set or malfunctioning thermostat can fail to signal the blower to activate.

What tells the furnace fan to turn on?

To put it very simply, the furnace fan limit switch is a control that tells your furnace's fan when to turn on and off.

Why is my blower motor not getting any power?

Make sure that the power cord hasn't melted or a fuse hasn't been blown. If your cables are looking fine, try unplugging the fan for a few minutes and then plugging it back in again. Sometimes, this process can reset the motor and solve your furnace problems.

How much does it cost to replace a blower motor?

Replacing a furnace blower motor costs $560, on average. Depending on the size and type of motor, most people pay $300 to $900. The average blower motor replacement cost is $560, but the final price depends on labor fees, as well as the cost of the parts.

How do I know if my AC blower fuse is bad?

Blowing the fuse cuts the power to the unit to prevent electrical damage. If your AC has shut down and won't start again, especially if you've noticed odd electrical behavior immediately before the shutdown, chances are the fuse has done its job and will need to be replaced.

How do I tell if my AC blower motor is bad?

6 Signs of a Bad AC Blower Motor
  1. Weak Airflow From Your Vents. One of the first signs you may notice is what feels like less air coming from your vents. ...
  2. No Airflow. ...
  3. Unusual and Loud Sounds. ...
  4. Climbing Utility Bills. ...
  5. Overheating. ...
  6. Tripping Circuit Breaker.

How to reset blower motor fuse?

How to Reset the HVAC Blower Sleeper Fuse
  1. Locate Fuse Box. You should first start by finding the fuse box which powers your HVAC system. ...
  2. Remove the Fuse. ...
  3. Inspect for Damage. ...
  4. Replace the Fuse. ...
  5. Close the Panel and Test for System Function. ...
  6. Call an Expert if the Fuse Reset Doesn't Work.

How do I know if my HVAC control module is bad?

Since the module regulates the entire AC system, inconsistent cooling, out-of-date software, and uneven air distribution are typical signs of a broken AC control module.

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