electrical

Blower Motor Control Module

for 1966 Chevrolet Corvette 327ci V8 · RWD

Difficulty

Easy

Time

1.4 h

Tools

Steps

This procedure covers the removal and replacement of the blower motor control module (resistor assembly) on a 1966 Chevrolet Corvette, which controls fan speed for the heater/defroster system.

Warnings

⚠Disconnecting the battery will erase radio presets and clock settings.

ℹ️The blower motor resistor is located in the engine compartment on the firewall, passenger side. Access is tight but does not require major disassembly.

⚠Inspect the resistor connector for heat damage or melting. A damaged connector indicates a chronic overheating issue that must be addressed.

Tools required

1/4 inch socket setEssential

Phillips screwdriverEssential

Flat blade screwdriver

Needle nose pliers

Work light or flashlightEssential

Wire brush or contact cleaner

Parts

Blower motor resistor assembly × 1 — Use OEM specification
Blower motor resistor connector (if damaged) × 1 — Use OEM specification

Preparation

Park vehicle on level surface and engage parking brake
Turn ignition off and remove key
Disconnect negative battery cable to prevent electrical shorts
Allow blower motor to cool if vehicle has been recently operated
Position work light to illuminate firewall area on passenger side of engine compartment

Procedure

1
Locate the blower motor resistor
Open the hood and locate the blower motor resistor assembly on the firewall, passenger side of the engine compartment. The resistor is mounted to the heater plenum with the wire connector facing outward. It is positioned above and slightly forward of the blower motor itself.
2
Disconnect the wiring harness
Locate the wiring connector(s) attached to the resistor assembly. Disconnect the push-on spade terminals or connector by pulling straight out; there may be no locking tab on this era of connector. If the connector is stubborn due to corrosion, gently work it side to side while pulling. Do not pull on the wires themselves.
3
Inspect the connector and wiring
Examine the connector terminals and the resistor terminals for signs of heat damage, corrosion, or melting. Check that all wire terminals are tight in the connector body. If the connector shows heat damage or the pins are loose, the connector must be replaced along with the resistor to prevent recurrence.
4
Remove the resistor mounting screws
Remove the 2 sheet metal screws securing the resistor assembly to the heater plenum. These are typically Phillips head screws. Keep these screws in a safe location as they will be reused.
5
Remove the resistor assembly
Pull the resistor assembly straight out from the heater plenum. The resistor has a rubber seal or gasket around its base that fits into the plenum opening. Gently work the assembly free if the seal is stuck.
6
Inspect the mounting area
Check the opening in the heater plenum for debris, leaves, or corrosion. Clean the mounting surface with a wire brush if necessary. Inspect the condition of the rubber seal on the old resistor to determine if it should be transferred to the new unit or if a new seal is required.
7
Prepare the new resistor
Compare the new resistor assembly to the old unit to verify correct application. Ensure the rubber seal is properly seated on the new resistor base. If reusing the old seal, carefully transfer it to the new resistor, ensuring it is clean and undamaged.
8
Install the new resistor assembly
Insert the new resistor assembly into the heater plenum opening, ensuring the rubber seal seats properly against the plenum housing. Align the mounting screw holes and push the assembly firmly into place.
9
Secure the resistor
Install the 2 mounting screws and tighten securely using a Phillips screwdriver. Do not overtighten as this may crack the resistor housing or strip the sheet metal threads. Screws should be snug with moderate hand pressure on the screwdriver.
10
Reconnect the wiring harness
Align the connector(s) with the resistor terminals and push firmly until fully seated. Gently tug on each connection to verify it is secure.
11
Reconnect the battery
Reconnect the negative battery cable and tighten the terminal clamp securely.

Reassembly

Verify all electrical connections are secure and properly locked
Ensure no tools or parts have been left in the engine compartment
Close hood after verification testing is complete

Verification

Turn ignition to the ON position without starting the engine
Test all blower motor speed settings (LOW, MEDIUM-LOW, MEDIUM-HIGH, HIGH) to verify proper operation
Verify smooth transition between speeds with no hesitation or intermittent operation
Listen for unusual noises from the blower motor during operation
After 2-3 minutes of operation on each speed, verify the resistor connector is not getting excessively hot (warm is normal, but it should not be too hot to touch)
Confirm airflow volume changes appropriately with each speed setting