Heater blower motors control the fan that offers airflow into the passenger area of the vehicle as well as running the heating and air conditioning systems of the vehicle.

How Do You Know You Have a Problem with your Heater Blower Motor?

The first symptom is a fan that makes strange noises such as squeaks or clanking which then may stop and the fan speed may then alter.

The second most common symptom is that you can hear the fan working, but there is no air coming through the vent.

The third symptom is that the fan only works on one speed which is high.  This is a clear indication that the blower motor resistor has broken and needs replacing.

If you find that your fan is continually running high, it means that there is no resistance in your blower motor resistor which means it may be time to replace it.  Fortunately this is easy and cost effective.

The first step is to locate your blower motor resistor in your vehicle and to assess which of the two types of resistor you have installed in your vehicle.

Types of Blower Motor Resisitors.

1.  In older vehicles, you will probably find that you have the wire coil type with various speeds generated by their own coil thickness.  The thicker the wire coil, the lower the speed.

2.  In more modern cars, you’ll find the circuit board transistorized version.

How to Change the Resistor Yourself.

The blower motor resistor is found under the dash board on the passenger side of the vehicle.  By laying down on the floor and looking up under the dash, you’ll easily locate it.  Removal and replacement is pretty simple, but if you are not sure about your electrical skills, it may be better to ask a professional to complete the task for you.

In order to complete the replacement you should have a voltmeter and a screwdriver handy.  You also want to check before replacing the blower motor resistor that it is definately the problem and that it is not a fuse that has blown.  This can be done by checking each of the fan controls individually to see which are working and which are not and then checking the fuses of those speeds that don’t work.  Fuses are generally located in the fuse and relay center under the hood.

Check the voltage of the electrical connector on the blower motor resistor to ensure that fuses are all good, check that you have power by turning the key and the fan on and then check the two terminals of the resistor.  If only one terminal has any power, the resistor needs replacing and if both the terminals have power then the problem generally lies with the motor itself and not the resistor.