Blower Motor Resistor
As part of your vehicle's heating and cooling system, this motor resistor is what allows the heater or A/C to change the fan's speed. It what lets you set the blower motor speed from low to hi depending on your preference. Over time, however, this part can fail. Once this part malfunctions, don't be surprised if there's no air coming from the vents, and the blower motor only works on certain speeds (ie: only at the highest setting or only 2 out of 4 settings are functional). If you notice these signs, it's most likely time to get a new blower motor resistor. Fortunately, troubleshooting and replacing this component is easy. Simply follow the steps below:
Tools you'll need:
- Voltmeter or circuit tester
Step 1: Locate the blower motor resistor.
This resistor is usually located close to the blower motor that's under the dashboard. It's most likely held in place by a plate with two or four screws on it. You'll know it's the resistor you're looking at if an electrical connector with five to six wires is plugged onto it. The number of wires depends on your vehicle's make and model. It's best to consult your vehicle manual since the exact location of the resistor depends on the type of car you have.
Step 2: Test the fuse.
To troubleshoot a problematic blower motor resistor, you need to carefully inspect your vehicle's AC or heater assembly and pay special attention to the electrical circuits. If you don't see anything wrong upon inspection, you need to test the resistor. Start by testing the fuse while the engine is turned on with a 12-volt test light. To do this, simply attach the test light's clip lead to a bolt or any good ground. Then link the tester's probe to the fuse terminals. If both terminals are powered up, then the fuse is good. If not, then the fuse has to be replaced.
Step 3: Test the blower motor.
To test the blower motor for power, unplug it and repeat the previous step. Only this time, you will be attaching the testing probe to the motor's terminals. Repeat this process at all the different motor speeds. If all terminals are powered up, then the motor is still in good shape. If not, then it needs replacing.
Step 4: Check the voltage at the relay and electrical connector.
When testing the relay and electrical connectors, there should be electricity flowing into the resistor's two terminals. If one terminal doesn't receive power, then the resistor is worn out.
Replacing the blower motor resistor
Step 1: Remove the blower motor.
Usually located under the dashboard, remove the blower motor by unscrewing or unbolting the cover plate. Then unplug the connector to access the blower motor resistor.
Step 2: Remove the old resistor and attach the new one.
Simply pull out the resistor and plug in the new one.
Step 3: Reattach all the other parts you've removed.
Start by reattaching the connector into the blower motor. Then reinstall the motor, making sure that all its parts are not damaged or dislodged. Then reattach the cover plate by screwing or bolting it back in place.