Blower Motor Resistor

Remove and replace the HVAC blower motor resistor assembly, which controls fan speed operation. The resistor is located in the passenger footwell area behind the lower dash trim.

Warnings

Tools required

Parts

• HVAC blower motor resistor assembly × 1 — Mopar 4885482AC or equivalent

Preparation

1. Park the vehicle on level ground and engage the parking brake
2. Turn the ignition off and remove the key
3. Allow HVAC system to cool completely if vehicle was recently operated
4. Open the passenger door fully for access to the lower dash area

Procedure

1. 1

   Access the passenger footwell
   Position yourself in the passenger footwell area. Move the passenger seat rearward to maximum travel for improved access. Use a flashlight to locate the blower motor resistor. On the 2005 Viper consult the factory service manual for the exact HVAC housing location, as it is typically mounted on the HVAC/evaporator housing behind the lower passenger-side dash trim.
2. 2

   Locate the resistor assembly
   Identify the blower motor resistor assembly. It is a rectangular module with an electrical connector and cooling fins, mounted to the HVAC housing with 2 screws. The resistor is positioned to receive airflow from the blower motor for cooling purposes.
3. 3

   Disconnect the electrical connector
   Locate the electrical connector on the resistor assembly. Depress the locking tab on the connector and pull it straight off the resistor terminals. If the connector is difficult to access, use a small flathead screwdriver to carefully release the locking tab while applying gentle outward pressure on the connector body.
4. 4

   Remove the resistor mounting screws
   Using the appropriate size socket or nut driver with a short extension, remove the screws securing the resistor assembly to the HVAC housing (verify fastener size and count against the service manual, typically 2 screws). Note the orientation of the resistor and any alignment features before removal. Support the resistor with your other hand as you remove the final screw to prevent it from falling. Note: Resistor Screws (hand-snug into plastic housing; do not overtighten — verify spec if provided)
   Torque spec

   Resistor Screws2 Nm (1.5 lb-ft)
5. 5

   Remove the resistor assembly
   Carefully withdraw the resistor assembly from the HVAC housing. The resistor may have a foam seal or gasket around its perimeter. Note the condition of any sealing material for reuse or replacement during installation.
6. 6

   Inspect the mounting area
   Examine the resistor mounting surface on the HVAC housing for debris, corrosion, or damage. Check the condition of the foam seal or gasket. Clean the mounting surface with a dry cloth if needed. Inspect the electrical connector terminals for corrosion, heat damage, or loose pins that could indicate additional electrical issues.
7. 7

   Prepare the new resistor
   Remove the new resistor assembly from its packaging. Transfer any reusable sealing material from the old resistor if the new unit did not include it, or install the new seal if provided. Verify that the cooling fins are not damaged and the electrical terminals are clean.
8. 8

   Install the new resistor assembly
   Position the new resistor assembly into the HVAC housing opening, ensuring proper orientation with cooling fins positioned to receive blower motor airflow. Align the mounting holes with the threaded bosses in the housing. Install both mounting screws and tighten them evenly and snugly by hand using the appropriate size socket or nut driver, taking care not to overtighten in the plastic housing. Do not overtighten, as this can damage the resistor housing or strip the mounting threads.
   Torque spec

   Resistor Screws2 Nm (1.5 lb-ft)
9. 9

   Reconnect the electrical connector
   Push the electrical connector firmly onto the resistor terminals until you hear or feel the locking tab engage. Verify the connection is secure by gently tugging on the connector body. Ensure the wiring harness is not pinched or stressed and has adequate clearance from any moving or hot components.

Reassembly

1. Return the passenger seat to the desired position
2. Ensure no tools or parts are left in the passenger footwell area

Verification

• Turn the ignition to the ON position without starting the engine
• Test all blower motor fan speed settings (typically 4 speeds plus off) to verify proper operation at each setting
• Listen for smooth motor operation without unusual noise or hesitation
• Verify that airflow volume increases appropriately with each higher speed setting
• Start the engine and retest all fan speeds under normal operating conditions
• After 5 minutes of operation on high speed, verify the resistor area is not producing burning odors or excessive heat beyond normal operation

Related trouble codes on this vehicle

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