Replace the blower motor resistor assembly located in the heater/ventilation system to restore proper fan speed control for interior climate comfort.

Warnings

Tools required

Parts

• Blower motor resistor assembly × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and set parking brake
2. Turn ignition off and remove key
3. Disconnect negative battery cable to prevent electrical shorts during repair
4. Allow blower motor system to cool if recently operated

Procedure

1. 1

   Access the resistor location
   The blower motor resistor is mounted on the heater blower housing on the engine side of the firewall, passenger's side (the same side as the blower motor). On A/C-equipped cars it is near the heater/evaporator housing. From the engine compartment, locate the resistor assembly on the passenger-side blower motor housing where the wiring connects to the heater fan. It is positioned on the blower housing with visible wire connections and may require reaching down behind the housing to access.
2. 2

   Disconnect the wiring harness
   Locate the electrical connector attached to the blower motor resistor. Depending on configuration, this may be a multi-pin connector or individual wire terminals. If equipped with a plug connector, squeeze the release tab and pull the connector straight off. If equipped with individual spade terminals, carefully pull each terminal connector off the resistor posts using needle-nose pliers if necessary. Note the wire color positions for reassembly.
3. 3

   Remove the resistor mounting fasteners
   Remove the screws securing the blower motor resistor to the heater housing (typically 2 small sheet metal screws). Verify the correct driver size by checking the hex head before applying force; these are commonly 1/4" or 5/16" hex on GM heater resistors of this era. Keep track of the screws as they are small and can easily be dropped into the engine compartment.
4. 4

   Extract the resistor assembly
   Carefully pull the blower motor resistor assembly straight out from the heater housing. The resistor may have a gasket or seal that causes it to stick slightly. If necessary, gently work a flathead screwdriver around the edges to break the seal, being careful not to damage the mounting surface on the housing.
5. 5

   Inspect the mounting area
   Examine the resistor mounting surface on the heater housing for corrosion, carbon buildup, or damage. Clean the mounting surface with a wire brush or sandpaper if corrosion is present. Check the wiring terminals for heat damage, melting, or loose connections. Inspect the blower motor housing opening for debris or blockage that might restrict airflow across the resistor.
6. 6

   Prepare the new resistor
   Compare the new resistor to the old unit to verify correct replacement. Check that all terminal posts match in number and position. If the new resistor includes a mounting gasket or seal, ensure it is properly positioned on the resistor body. If no gasket is provided and the old gasket is in good condition, it may be reused.
7. 7

   Install the new resistor assembly
   Position the new blower motor resistor into the mounting opening in the heater housing, ensuring the gasket seats properly against the housing surface. Align the mounting screw holes. The resistor element side must face into the blower motor housing airflow for proper cooling.
8. 8

   Secure the resistor mounting fasteners
   Install the mounting screws and tighten securely using the correct hex driver verified during removal (commonly 1/4" or 5/16" hex on GM heater resistors of this era). Tighten evenly to compress the gasket and ensure a proper seal. Do not overtighten as this may strip the sheet metal threads or crack the resistor body. The screws should be snug but not excessively tight.
9. 9

   Reconnect the wiring harness
   Reconnect the electrical connector to the blower motor resistor. If using a plug-style connector, push firmly until you hear or feel a positive click indicating the locking tab has engaged. If using individual spade terminals, push each terminal connector fully onto the corresponding resistor post, ensuring they are seated firmly. Verify wire positions match the original configuration noted during disassembly.
10. 10

    Reconnect battery and test operation
    Reconnect the negative battery cable. Turn the ignition to the ON position (engine does not need to run). Test the blower motor operation at all available speed settings (the 1966 Corvette typically has LOW, MEDIUM, and HIGH). Verify that each speed setting produces a distinct and appropriate blower motor speed. Listen for unusual noises or intermittent operation that might indicate poor connections.

Reassembly

1. Ensure all electrical connections are secure and properly seated
2. Verify no tools or hardware were left in the engine compartment
3. Confirm blower motor operates correctly at all speed settings

Verification

• With engine running and ventilation system on, test each blower speed setting and confirm distinct speed changes
• Verify LOW and MEDIUM speeds now function properly (these are the speeds most commonly affected by resistor failure)
• Check that no burning smell is present during blower operation, which would indicate poor resistor mounting or inadequate airflow
• Confirm all speed settings produce steady airflow without intermittent operation or motor cycling

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