Mechanics

Blower Fan Motor Works On High Speed Only

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Step by step repair guide on how to repair a blower motor that only works on the high speed setting. This article pertains to all non climate controlled vehicles.

Difficulty Scale: 3 of 10

Tools and Supplies Needed

  • Flashlight
  • Socket Set
  • Screw Driver Set
Begin by parking the car on level ground in park with the emergency brake on.


Air Vent
Step 1 - Turn the key to the "on" position (do not start the engine). Inspect system fuse and replace if needed. Some cars utilize a separate fuses to control lower fan speeds in the fuse box, inspect all fuses and replace if failed.

Step 2 - Locate and remove the fan speed resistor component. This resistor is almost always located in the heater plenum so it can be cooled by air circulating in the system. After the resistor is removed inspect the resistor for obvious burn marks. If an area shows signs of extreme heat (burned) it needs to be replaced. Also inspect the resistor connector for heat damage. Reinstall with new and recheck system.

Helpful Information

A blower fan motor pushes air throughout the ventilation system. This air is processed by a series of doors and vents to direct the air to various positions: heater, air conditioner and defrost modes. Most blower motors are powered by a basic electrical circuit that utilizes a multi speed resistor or a solid-state resistor to control different fan speed modes (low, medium low, medium and high). If the resistor malfunctions it may lose one or more of the lower fan speed settings.

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AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-09-13)