Blower Motor Control Module

Replace the blower motor control module (also called blower motor resistor) that regulates HVAC fan speed in the 1994-2007 Dodge Ram 2500 with 5.9L Cummins diesel engine.

Warnings

Tools required

Parts

• Blower motor control module (resistor) × 1 — Use OEM specification or equivalent (Mopar 4885482AC or equivalent)
• Electrical connector grease (dielectric grease) × 1 — Small packet

Preparation

1. Ensure the ignition is OFF and the key is removed
2. Allow HVAC system to cool if recently operated
3. Position yourself comfortably to work under the passenger side dashboard
4. Test blower motor operation on all speeds to confirm failure pattern before beginning work

Procedure

1. 1

   Disconnect battery negative terminal
   Disconnect the negative battery cable to prevent electrical shorts during the repair. Use a 10mm wrench or socket to loosen the terminal bolt. Tighten to specification upon reassembly. Use OEM specification or equivalent (verify correct part number for your specific model year via Mopar catalog or parts supplier).
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
2. 2

   Access blower motor control module area
   Locate the blower motor control module on the passenger side of the vehicle, underneath the dashboard. It is mounted on the HVAC housing near the blower motor itself, typically on the right side of the plenum chamber. You may need to remove the passenger side under-dash panel or insulation for better access depending on model year. On most Ram 2500s, you can reach it by working from the passenger footwell area.
3. 3

   Locate and identify the control module
   Depending on model year and HVAC type, the part is either a blower motor resistor (a small ceramic/wire-wound resistor block with several coils) or, on models with automatic temperature control, a finned aluminum solid-state control module approximately 3-4 inches long. It will have an electrical connector plugged into it and will be mounted to the HVAC housing with screws. Use a flashlight to positively identify the correct part before proceeding. It will have an electrical connector plugged into it and will be mounted to the HVAC housing with two screws. Use a flashlight to positively identify the module before proceeding.
4. 4

   Disconnect electrical connector
   Depress the locking tab on the electrical connector and carefully pull the connector straight off the module. If the connector is stuck due to corrosion, gently wiggle it while pulling. Do not pry on the connector body itself. Inspect the connector terminals for corrosion, melting, or discoloration.
5. 5

   Remove module mounting screws
   Remove the two screws that secure the blower motor control module to the HVAC housing using a 7mm socket or nut driver. These screws may be difficult to access due to limited space. Keep track of these screws as they are easily dropped in the plenum area.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
6. 6

   Remove old control module
   Carefully pull the blower motor control module out of its mounting position. The module has electrical prongs that insert into the connector, so pull it straight out without twisting. Inspect the old module for signs of overheating, burned components, or melted plastic.
7. 7

   Inspect and clean mounting area
   Inspect the HVAC housing mounting surface for damage, debris, or corrosion. Clean the mounting surface with a cloth to ensure proper contact and heat dissipation. Check that the screw holes are not stripped or damaged.
8. 8

   Inspect electrical connector
   Carefully inspect the vehicle-side electrical connector for melted terminals, corrosion, or damage. Clean the terminals with electrical contact cleaner if necessary. If terminals show severe damage or melting, the connector pigtail should be replaced before installing the new module.
   ⚠A damaged connector can cause the new module to fail prematurely. Do not install a new module if the connector is melted or severely corroded.
9. 9

   Install new blower motor control module
   Position the new blower motor control module into the mounting location on the HVAC housing. Ensure the electrical prongs align properly with the mounting holes and that the heat sink fins are oriented to allow air flow. The module should sit flush against the mounting surface.
10. 10

    Install mounting screws
    Thread the two mounting screws by hand first to ensure proper thread engagement. Tighten the screws evenly and snug by hand with a nut driver until seated; these small screws thread into plastic and have no published torque spec, so do not overtighten. Do not overtighten as this can crack the module housing or strip the plastic HVAC housing threads.
    Torque spec

    Module Mounting Bolts8 Nm (6 lb-ft)
11. 11

    Apply dielectric grease and reconnect connector
    Apply a small amount of dielectric grease to the electrical terminals on the new module to protect against corrosion. Push the electrical connector firmly onto the module until you hear or feel the locking tab click into place. Gently tug on the connector to verify it is locked.
12. 12

    Reconnect battery
    Reconnect the negative battery cable and tighten the terminal clamp bolt securely (typically about 5 ft-lbs / 7 Nm). Ensure the connection is clean and secure. Ensure the connection is clean and secure.
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Reinstall any under-dash panels or insulation that were removed for access
2. Ensure no tools or parts are left in the passenger footwell area
3. Clean up any debris or dropped hardware from the work area

Verification

• Turn the ignition to the ON position (engine does not need to be running)
• Test the blower motor on all fan speed settings (LOW, MEDIUM-LOW, MEDIUM-HIGH, HIGH) to verify proper operation at each speed
• Listen for unusual noises from the blower motor that might indicate other issues
• Verify that air flow corresponds correctly to the selected fan speed
• Check that the blower motor turns off completely when switched to OFF position
• Allow the system to run for several minutes on each speed setting to confirm the new module does not overheat
• Monitor for any burning smell which would indicate electrical problems

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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