Blower Motor Testing Guide

Step by step guide on how to test a typical blower fan motor for a car air conditioner, heater and defroster modes. When this motor stops working one of three things has happened, either the electrical supply has stopped, the motor has burned out or the system ground has failed. This guide will explain troubleshooting steps that will help you repair the problem. This article pertains to most cars.

Before you begin sit back and watch this video we have made for you on how to replace a car blower motor, then continue down the guide for additional information.

Difficulty Scale: 4 of 10

Tools and Supplies Needed

  • Test light
  • Basic tool set
  • Protective eyewear and clothing
Begin by parking the automobile on level ground with the parking brake set.

Step 1

This motor unitizes power from a fuse or relay in the fuse panel. With the ignition key in the on position test the fuse which can be identified by the fuse box cover or in the vehicles owners manual, if the fuses are okay, proceed to next step. Learn more

Step 2

With the key in the on position turn the fan switch to the high speed setting, then to the medium and low speeds. If the fan motor works in the high speed setting the speed resistor needs to be tested. Learn more

Step 3

Next, locate motor which is usually under the dash or hood on the passengers side.

Step 4

Locate and disconnect the motor wiring. Using a test light and a sharp metal object such as a hooked scribe to check for power at the connector (large wires).

This test confirms power and the ground of the circuit, if the test light illuminates continue to the next step. This test can also be used by piercing the wiring harness as well.

Note: Intermittent power failure from the heater switch, fuse holder or climate control relay could be a problem so even though the circuit has power, its best to test the motor itself.

If the test light fails to light up the ground or power circuit has shorted and a wiring schematic is needed to troubleshoot the problem further. If the motor only has one wire use a grounded test light for testing. Some vehicles are equipped with a blower motor relay which should also be checked.  Learn more

Step 5

Once power and ground have been confirmed, locate and remove the motor mounting bolts.

Step 6

Once all mounting bolts have been removed grasp the assembly and remove it for testing.

Step 7

Prepare a positive power and negative ground lead from a 12 volt power source (car battery). Use caution to not allow the clips to contact each other or sparks (heat) will occur.

Step 8

While grasping the motor firmly, attach the power and negative wiring clips to the wiring harness. If the unit only has a power lead attach the ground wire to the frame of the motor.

Once the circuit is completed the motor will spin or wont confirming the motor failure, these units typically fail intermittently.

If you have any question about what you just read please visit our forum where thousands of answers have been given by our online mechanics. Learn more


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