Identifying Symptoms of a Failing Automotive HVAC System Blower Motor

The HVAC system blower motor is an essential part of the air condition, defroster, fresh air intake and heater systems this motor is used to circulate air through the car while drawing fresh air to the car's interior from the outside. A blower motor is a basic 12 volt (DC) medium size electric motor that pulls a respectable amount of amperage (about 12 amps) which in time can burn out and stop working. As the blower motor ages the amperage that it requires to run the motor increases which overloads the electrical system and can cause additional problems which is due to normal bearing and brush wear that occurs in all motors of this type.

When this heater motor stops working one of three things has happened, the electrical supply has quit, the motor has burned out or the system ground has failed, the internal bearings have worn out or require lubrication. This guide will walk you through the common symptoms of a bad HVAC blower motor and provide detailed steps to diagnose the issue.

Popular Failure Symptoms

1. Intermittent Air Flow: Anytime a DC electrical motor starts to go bad due to worn brushes, (which is the most popular failure) the motor will start and stop "at will" when the system is on, especially after the car experiences a bump in the road.

2. Low Air Flow: The intensity of the blower motor output will start to fade (low vent air flow) as the integrity of the internal motor parts start to wear and overheat, even thought the motor is still working it's performance is diminished and should be replaced.

3. Overheated Electrical Components: A overheated fuse holder, blower fan motor, high speed relay, fan speed control module or the fan speed resistor electrical connectors will be a result of excessive amperage being pulled through the motor which will cause the circuit to stop working.

4. Vent Burning Smell: A burning small can be present through the vents as the blower motor windings overheat and cook the insulation resulting in a smell of burnt plastic.

5. Motor Bearing Failure: The armature of the blower motor is supported by bearings or bushings which can fail and cause the blower motor to produce an audible squeak or squeal when in use. This can sometimes be fixed by adding lubrication such as WD40. This is a sign that the blower fan motor is going bad and needs replacing.

Watch the Video!

Please watch this video of the job being done to glean additional helpful information.

Credits

This guide knowledge base was created by the 2CarPros Team, and by Ken Lavacot: Automobile repair shop owner and certified master automobile technician of over 30 years. If you have question or need help please ask one of our experts we are happy to help. Please visit our 2CarPros YouTube Channel.