Fan blower motor not working? We are a team of ASE certified mechanics that
have created this guide to help replace a burned out blower motor and test the
electrical system that powers it. This guide will also show you what you
are paying for when taking your car in for repairs.
What Goes Wrong?
A blower motor is a basic 12 volt (DC) medium size electric motor that pulls a
respectable amount of amperage (about 15 amps) which in time can burn out and
stop working. As the blower motor ages the amperage that it takes to run the
motor increases that overloads the electrical system which can cause additional
problems. This is due to normal bearing and brush wear that occurs in all
motors of this type. This wear can sometime be correlated to an audible ticking
or squeaking noise when the fan is operating.
When this heater motor stops one of three things has happened the
electrical supply has quit, the motor has burned out or the system ground has
failed. A sign that the motor is going bad is when the system is on and the car hits
a bump and the motor will start to work. This is telling you the brushes have
worn out and the blower motor needs replacing.
This Guide Includes
Blower motor replacement
Blower motor testing
Electrical circuit testing
Let's Get Started!
The blower motor can be located in one of two places which is under the dash
or hood on the passenger side of the vehicle. There is one blower motor that
works for all climate control modes: air conditioner, heater and defroster. Some
manufactures make accessing this motor difficult and you will need to remove the
complete or a portion of the heater plenum (box) for replacement, this is not
Step 1: Accessing the Blower Motor
Start by checking under the hood and looking around the passenger's side for
something that looks like this:
If you cannot find the blower motor under the hood it will be located under
the dash on the passenger side. You may need to remove the mounting screws of the lower panel to gain access to the motor
This heater motor location is under the dash. Let's start the removal which is
the same for under hood or dash applications.
Step 2: Remove the Blower Motor
Locate and disconnect the a/c blower motor wiring by releasing the safety tab on
the side of the connector. This connector can have one or four wires depending
if the system is manually or automatically controlled. These different systems
will vary the fan speed by using a solid state speed controller
apposed to a basic resistor.
Once the electrical connector is removed check its condition while looking for corrosion or
burned terminals which are a sign of high resistance or increased amperage draw.
If the connector is melted it must be replaced by splicing in a new part which
you can get from the dealer, auto parts store or Amazon. Opposed to a crimp
connector, it's best to solider these wires together to cut down on resistance which helps the
motor last longer.
Identify the heater motor and the mounting screws holding it into the heater
box. These screws are mounted in the plastic housing and are not to terribly
tight so they can be removed easily. Some of these screws can be hidden
under metal braces, plastic tabs or wiring so use a small mirror if needed.
Start by removing the mounting screws one at a time. The motor will then start
to fall out of the heater box. While holding the blower motor in place remove
the last screw.
After all of the screws have been undone grasp the motor and remove it from the
housing. This can take some maneuvering so hang in there and be careful not to
damage the fan blade (squirrel cage) against the heater plenum.
Step 3: Install the New Blower Motor
Once the old motor has been removed compare it to the new unit. In some cases an
electronic speed controller is used in climate controlled systems and will need
to be transferred to the new motor but this is not typical. On some replacement units you will need to transfer the old fan
blade over to the new assembly. This is done by removing the mounting nut or
clip and then forcing the blade off of the motor shaft using a large standard
screwdriver. Do not use oil or lube
of any kind to help installation of the fan onto the replacement motor because
it will allow the fan to slip on the shaft which will create problems.
Before installing the new motor into the plenum check for obvious obstructions
such as leaves, sticks, ink pens, tooth picks or small toys which can get into
the system via the inlet or outlet vents. These foreign partials can keep the
motor from working freely and could cause premature failure.
When the new assembly is ready to be installed fit the motor by maneuvering and rotating it gently.
Then push it back into the plenum while lining up the mounting holes.
While the motor is in place start to install the mounting screws while holding
it toward the plenum. Do not tighten any of the screws until all
screws have been threaded in by hand. This will make the installation go mush
easier without the potential of stripping the screws out.
Tighten each screw in a cross pattern, do not over tighten. This will ensure the proper alignment of the fan blade in the
housing. If this step is not done properly it can cause the blade to contact the
housing creating a rubbing or clicking noise when the motor is operating.
Check the wiring connector locating tang
which indicates the orientation of the connector before it's installed into the
motor. This tang is to ensure you don't install the connector incorrectly which
would cause electrical problems.
Then carefully re-insert the blower fan motor electrical connector by securing it into
position. You should hear an audible click telling you the connector is
installed correctly. Gently tug on the wiring to ensure its correct
installation. Then reinstall the lower dash cover and install the mounting
screws by hand. Tighten them snuggly, do not over tighten, again these screws
are going into plastic.
Finally start the engine up and turn the climate control on and listen for the
fan to come on. It should sound smooth and be blowing from the vents in a strong
flow. If you hear a rattle, squeak or ticking turn the system off and remove the
blower motor to recheck the installation.
Watch the Video!
Here is a video of the blower motor getting replaced.
Testing the Blower Motor and Electrical System
Start testing by turning the ignition switch to the on position throughout
this test procedure.
Step 1: Check the Blower Fan Operation
With the key in the on position turn the fan switch to the high speed
setting, then to the medium and low speeds to test its performance.
Feel the flow of the air coming out of the vents if no air is felt then
continue with this guide.
Step 2: Check the Electrical System
The blower fan unitizes power from a
fuse or relay in the fuse panel. With the ignition key in the on position
the fuse which can be identified by the fuse box cover or in the vehicles owner's
manual. If the fuses are okay, proceed to next step. If the fuse is blown
replace the fuse with a new one. If the new fuse blows nine times out of ten the
problem is the blower motor which has developed a short and needs replacement.
Some vehicles are equipped with a
blower motor relay which should also be checked. Other possibilities for a
short are a system wiring failure.
Locate and disconnect the motor wiring connector. Use 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 then power is getting to the blower motor which is telling you the blower motor
is bad. This test can also be used by piercing the wires of the wiring harness
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 blower motor only has one wire
it is used for power. In this case a grounded test light is used for testing.
Step 3: Test the Blower Motor
To test the motor 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 and 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 or wont spin confirming the motor
failure. These units typically fail intermittently. Intermittent power failure from the
heater switch, fuse holder or climate control relay could also be a problem so even though the circuit might currently have power.
Blower Fan Works on High Only
This is a classic blower motor resistor problem which is common on older cars and trucks
that use manual fan speed switch controls. This problem will also occur on
climate control systems when the speed controller has burned out omitting full
power to the blower motor. This can also occur with the ignition key off.
When the blower fan is switched onto the high speed setting the circuit uses a straight
connection from positive and negative battery power. When the motor
is switched onto the lower speeds the electrical power is routed through a series
of resistors or a solid state assembly that drops the voltage down to 6 volts, 8
volts and then 10 volts (low, medium low, medium) which in turn makes the blower motor turn
Step 1: Locate the Resistor
The location of this resistor is usually near the blower motor itself which cools the
unit when it's in operation. Both of these parts are located in the heater plenum box
either inside the vehicle on the passenger side or under the hood mounted near
the firewall on the passenger side.
Step 2: Test the Resistor
grounded test light and locate the outgoing wire
from the resistor to the blower motor (usually orange or red). While moving the
switch to each fan speed test for power. If there is no power on any of the lower speeds the resistor has failed
and needs replacement.
Below is a typical wiring diagram for the blower motor circuit which is
basically the same for all vehicles utilizing this manual system.
Step 3: Replace the Resistor
Turn the ignition key off and remove the fan resistor to inspect for burn
marks which are an indication of failure. If an area shows signs of extreme heat
(burned) it needs to be replaced. Also inspect the resistor connector for heat
damage at the terminals and replace or repair it as needed by splicing in a new
connector. Anytime you replace the resistor its a good
idea to replace the blower motor as well to prevent premature failure due to
high amperage draw.