Introduction
This manual provides essential information for the installation, operation, maintenance, and troubleshooting of the Standard Motor Products RU-638 Blower Motor Resistor. This component is crucial for regulating the fan speed of your vehicle's heating, ventilation, and air conditioning (HVAC) system.
The RU-638 Blower Motor Resistor is designed to provide reliable performance and ensure proper functionality of your vehicle's climate control system.
Safety Information
Always prioritize safety when working on automotive electrical systems. Failure to follow safety precautions can result in serious injury or damage to the vehicle.
- Disconnect Battery: Before beginning any work, always disconnect the vehicle's negative battery terminal to prevent electrical shock or short circuits.
- Professional Installation Recommended: Installation of automotive electrical components can be complex. If you are not experienced with automotive repairs, it is highly recommended to seek assistance from a qualified mechanic.
- Wear Protective Gear: Use appropriate personal protective equipment, including safety glasses and gloves.
- Consult Vehicle Manual: Refer to your vehicle's specific service manual for detailed instructions and diagrams related to the blower motor resistor location and replacement procedure.
Setup and Installation
The Standard Motor Products RU-638 Blower Motor Resistor is designed as a direct replacement part. The exact installation procedure may vary depending on your vehicle's make and model. The following steps provide a general overview.
- Locate the Resistor: The blower motor resistor is typically located near the blower motor, often under the dashboard on the passenger side, or sometimes in the engine bay. Consult your vehicle's service manual for the precise location.
- Disconnect Electrical Connector: Carefully disconnect the electrical connector(s) from the old blower motor resistor.
- Remove Mounting Screws: The resistor is usually held in place by a few screws (often Torx screws). Remove these screws to detach the old resistor.
- Install New Resistor: Position the new Standard Motor Products RU-638 resistor in place and secure it with the mounting screws. Ensure it is seated properly.
- Reconnect Electrical Connector: Reconnect the electrical connector(s) to the new resistor, ensuring a secure connection.
- Reconnect Battery: Reconnect the vehicle's negative battery terminal.
- Test Functionality: Turn on the vehicle's ignition and test the blower fan at all speed settings to confirm proper operation.
Figure 1: Front view of the Standard Motor Products RU-638 Blower Motor Resistor, showing the heat sink fins and electrical connector.
Figure 2: Side view of the Standard Motor Products RU-638 Blower Motor Resistor, highlighting the mounting tabs and overall compact design.
Operating the Blower Motor Resistor
The RU-638 Blower Motor Resistor operates passively within your vehicle's HVAC system. Its function is to provide varying levels of electrical resistance to the blower motor, thereby controlling the speed at which the fan operates.
- When you select a lower fan speed on your vehicle's climate control, the resistor introduces more resistance, reducing the voltage supplied to the blower motor and causing it to spin slower.
- As you increase the fan speed, less resistance is applied, allowing more voltage to reach the motor, resulting in faster fan operation.
- Typically, the highest fan speed setting bypasses the resistor entirely, providing full battery voltage directly to the blower motor for maximum airflow.
Proper operation of the resistor ensures that you can effectively control the airflow within your vehicle's cabin for heating, cooling, and ventilation.
Maintenance
The Standard Motor Products RU-638 Blower Motor Resistor is a sealed electronic component and is not designed for user maintenance or repair. Its internal components are not serviceable.
- Inspection: Periodically, during other automotive maintenance, you may visually inspect the resistor and its wiring for any signs of corrosion, melting, or damage.
- Cleaning: Keep the area around the resistor free from debris and excessive dust, which could potentially impede heat dissipation.
- Replacement: If the resistor fails, it must be replaced with a new unit. Attempting to repair a faulty resistor is not recommended and can be unsafe.
Troubleshooting
If your vehicle's blower fan is not operating correctly, the blower motor resistor may be the cause. Here are common symptoms and troubleshooting steps:
| Symptom | Possible Cause | Solution |
|---|---|---|
| Blower fan only works on high speed. | Resistor has failed, often due to overheating, causing the lower speed circuits to open. | Replace the blower motor resistor. |
| Blower fan does not work on any speed. | Blown fuse, faulty blower motor, or completely failed resistor. | Check the relevant fuse in your vehicle's fuse box. Test the blower motor directly. If both are fine, replace the resistor. |
| Blower fan works intermittently. | Loose electrical connection, intermittent resistor failure, or failing blower motor. | Inspect all electrical connections to the resistor and blower motor. Consider replacing the resistor if connections are secure. |
Important: If troubleshooting does not resolve the issue, or if you are unsure about performing these steps, consult a certified automotive technician for diagnosis and repair.
Specifications
Key specifications for the Standard Motor Products RU-638 Blower Motor Resistor:
| Model Number | RU-638 |
| Manufacturer Part Number | RU-638 |
| Brand | Standard Motor Products |
| Connector Type | Screw |
| Contact Type | Normally Open |
| Mounting Type | Surface Mount |
| Number of Terminals | 2 |
| Item Weight | 7 ounces |
| Product Dimensions | 5.19 x 5.19 x 2.5 inches |
| Country of Origin | China |
| UPC | 025623955919 |
Warranty and Support
For specific warranty information regarding the Standard Motor Products RU-638 Blower Motor Resistor, please refer to the warranty documentation provided with your purchase or visit the official Standard Motor Products website. Warranty terms and conditions may vary.
If you require technical assistance or have questions not covered in this manual, please contact Standard Motor Products customer support or the retailer from whom you purchased the product. Have your product model number (RU-638) and purchase details ready when contacting support.