Blower motor resistors are small but essential components in your HVAC system. They regulate the speed of the blower motor, which in turn affects the airflow throughout your home. Over time, blower motor resistors can fail, leading to a number of problems, including reduced airflow, overheating, and even electrical fires. Fortunately, replacing a blower motor resistor is a relatively simple and inexpensive task that can be completed in a few hours.
The first step is to identify the location of the blower motor resistor. It is typically located in the blower compartment, which is usually found near the furnace or air handler. Once you have located the blower motor resistor, you will need to disconnect the power to the HVAC system. This can be done by turning off the circuit breaker or fuse that supplies power to the system. Next, remove the cover of the blower compartment and locate the blower motor resistor. It is typically attached to the blower motor with a few screws.
Once you have located the blower motor resistor, you will need to disconnect the wires that are connected to it. Be sure to label the wires so that you can reconnect them correctly later. Once the wires are disconnected, you can remove the blower motor resistor from the blower motor. The new blower motor resistor can then be installed in the reverse order of the removal process. Be sure to tighten the screws that secure the blower motor resistor to the blower motor and reconnect the wires. Finally, turn on the power to the HVAC system and test the blower motor to make sure that it is working properly.
Assessing the Blower Motor Resistor Damage
Diagnosing a faulty blower motor resistor requires a systematic approach. Here are some key steps to follow:
1. Troubleshooting the Blower Motor:
Before delving into the resistor, ensure the blower motor itself is functioning properly. Check if the motor is receiving power by connecting a multimeter to its leads. If there’s no power, inspect the wiring and connections for any faults.
2. Identifying the Resistor Location:
Locate the blower motor resistor, typically positioned near the motor or inside the HVAC control module. Refer to the vehicle’s service manual or online resources for specific instructions on its location. The resistor usually has multiple terminals and a distinct shape, making it easy to identify.
| Fault Description | Possible Causes |
|---|---|
| No air flow from any speed setting | Faulty blower motor or resistor |
| Fluctuating air flowDefective resistor or intermittent connection | |
| Air flow only on high speed | Open circuit in resistor or wiring issue |
3. Visual Inspection:
Carefully inspect the resistor for any visible signs of damage, such as burn marks, cracks, or loose connections. A burnt resistor typically indicates a short circuit, while loose connections can cause intermittent airflow issues.
4. Electrical Testing:
Use a multimeter to measure the resistance across the resistor terminals. Compare the measured value with the specifications provided in the vehicle’s manual. A significant deviation from the specified value indicates a faulty resistor.
Tools Required for Replacement
Replacing a blower motor resistor requires a few basic tools. Here’s what you’ll need:
Flashlight
A flashlight is essential for illuminating the work area, especially if you’re working in a dimly lit area or under the dashboard.
Screwdriver (Phillips head)
You’ll need a Phillips head screwdriver to remove the screws that secure the blower motor resistor in place.
Wrench (10mm)
A 10mm wrench is needed to loosen the nuts that hold the electrical connectors in place.
Electrical tape
To ensure a secure and weatherproof connection, you’ll need electrical tape to wrap around the wire connectors after reattaching them.
Gloves
To protect your hands from sharp edges or electrical components, it’s recommended to wear gloves while handling the blower motor resistor.
Digital multimeter (optional)
A digital multimeter can be used to test the continuity of the blower motor resistor and ensure it’s functioning properly before installing it.
Safety glasses
To protect your eyes from flying debris or electrical sparks, it’s advisable to wear safety glasses when working with electrical components.
Additional Tips for Using a Multimeter
If you’re using a digital multimeter to test the blower motor resistor, here are a few additional tips:
| – Set the multimeter to the ohms scale. |
| – Touch the probes to the terminals of the resistor. |
| – A reading of 0 ohms indicates a short circuit, while a reading of infinity indicates an open circuit. |
| – If the reading is within the specified range for the resistor, it’s considered functional. |
Removing the Blower Motor Housing
To access the blower motor resistor, you need to remove the blower motor housing. This can be a tricky process, so it’s important to follow these steps carefully.
1. Disconnect the Negative Battery Terminal
Safety first! Before you start working on the blower motor, disconnect the negative battery terminal. This will prevent any electrical accidents.
2. Locate the Blower Motor Housing
The blower motor housing is usually located under the dashboard, on the passenger side of the vehicle. It’s a rectangular box with a few wires and hoses connected to it.
3. Remove the Screws
Use a screwdriver to remove the screws that hold the blower motor housing in place. There may be several screws, so be sure to get them all.
4. Disconnect the Wires and Hoses
Once the screws are removed, you need to disconnect the wires and hoses that are connected to the blower motor housing. Be careful not to damage any of the connectors.
5. Remove the Blower Motor Housing
Once the wires and hoses are disconnected, you can gently pull the blower motor housing out of its place. Be careful not to drop it or damage any of the components.
6. Locate the Blower Motor Resistor
The blower motor resistor is usually located inside the blower motor housing. It’s a small, rectangular component with a few wires connected to it. To remove the blower motor resistor, you need to:
- Disconnect the wires from the blower motor resistor.
- Remove the screws that hold the blower motor resistor in place.
- Pull the blower motor resistor out of its socket.
Once you have removed the blower motor resistor, you can install the new one in its place. Be sure to connect the wires and hoses properly, and then reinstall the blower motor housing.
| Step | Description |
|---|---|
| 1 | Disconnect the negative battery terminal. |
| 2 | Locate the blower motor housing. |
| 3 | Remove the screws. |
| 4 | Disconnect the wires and hoses. |
| 5 | Remove the blower motor housing. |
| 6 | Locate the blower motor resistor. |
Restoring Electrical Power and Testing the System
1. Reconnecting the Negative Terminal
Attach the negative terminal of the battery to its post and tighten the nut.
2. Tightening the Positive Terminal
Reattach the positive terminal, ensuring it’s secure and tightened.
3. Starting the Vehicle
Insert the key and start the vehicle.
4. Verifying Function
Check if the blower motor is now functioning as expected at various speed settings.
5. Checking for Leaks
Inspect the replaced blower motor resistor for any signs of leaks or damage.
6. Monitoring Operation
Observe the blower motor operation for a few minutes to ensure consistent and reliable performance.
7. Troubleshooting Potential Issues
If any issues persist, examine the wiring connections, inspect the blower motor, or consult a qualified mechanic for further diagnosis.
8. Reconnecting the Controls
Reinstall the controls and ensure they are securely attached and operational.
9. Testing System Function
Verify the blower motor and controls are working together seamlessly under various conditions.
10. Post-Repair Inspection
After an extended period of operation, inspect the blower motor resistor and surrounding components for any signs of damage or excessive heat.
How to Change a Blower Motor Resistor
A blower motor resistor is a small, electrical device that regulates the speed of a blower motor. It is typically located near the blower motor, and it is connected to the motor’s power supply. When the resistor is working properly, it will allow the motor to run at a consistent speed. However, if the resistor fails, it can cause the motor to run too slowly or too quickly, or it can even cause the motor to stop running altogether.
If you are experiencing any problems with the speed of your blower motor, you may need to replace the blower motor resistor. This is a relatively simple task that can be completed in a few minutes. Here are the steps on how to do it:
- Turn off the power to the blower motor.
- Locate the blower motor resistor. It is typically located near the blower motor, and it will be connected to the motor’s power supply.
- Disconnect the wires from the resistor.
- Remove the resistor from the mounting bracket.
- Install the new resistor in the mounting bracket.
- Connect the wires to the new resistor.
- Turn on the power to the blower motor.
- Test the blower motor to make sure that it is running at the correct speed.
People Also Ask
What are the symptoms of a bad blower motor resistor?
The symptoms of a bad blower motor resistor can include:
- The blower motor is running too slowly
- The blower motor is running too quickly
- The blower motor is not running at all
- The blower motor is making a strange noise
How do I test a blower motor resistor?
You can test a blower motor resistor with a multimeter. Set the multimeter to the ohms setting, and then touch the probes to the terminals of the resistor. The resistor should have a reading of between 0 and 10 ohms. If the reading is significantly higher or lower than this, then the resistor is likely bad.
How much does it cost to replace a blower motor resistor?
The cost to replace a blower motor resistor will vary depending on the make and model of your vehicle. However, the average cost is between $50 and $100.
