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
Difficulty Scale: 4 of 10
Tools and Supplies Needed
Basic tool set
Protective eyewear and clothing
Begin by parking the automobile on level ground with the parking brake set.
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.
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.
Next, locate motor which is
usually under the dash or hood on the passengers side.
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
Note: Intermittent power failure from the
fuse holder or
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
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.
Once power and ground have been confirmed,
locate and remove the motor mounting bolts.
Once all mounting bolts have been removed
grasp the assembly and remove it for testing.
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.
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.
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