Blend Door Actuator

This procedure guides the removal and replacement of the heater blend door actuator control cable on a 1966 Chevrolet Corvette, restoring proper temperature control functionality.

Warnings

Tools required

Parts

• Heater control cable assembly × 1 — Use OEM specification
• Cable retaining clips × 2 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Disconnect negative battery cable to prevent accidental short circuits while working near electrical components
3. Remove driver's side floor mat and protect interior surfaces with towels or drop cloths
4. Allow engine compartment to cool completely if vehicle was recently operated

Procedure

1. 1

   Remove lower dash panel access
   Working from inside the vehicle, locate and remove the lower dash panel on the driver's side. Remove the 4 Phillips head screws securing the panel. Carefully pull the panel down and away from the dash structure. Set aside with hardware.
2. 2

   Access heater control assembly
   Locate the heater control panel in the center dash area. Remove the 2 screws securing the control panel trim bezel. Gently pull the bezel forward to access the back of the control panel.
3. 3

   Disconnect control cable at dash end
   Behind the heater control panel, locate the temperature control lever mechanism. Note the routing and connection point of the cable. Use needle nose pliers to compress the cable housing retaining clip and slide it backward off the mounting bracket. Disconnect the inner cable wire from the temperature lever by sliding it out of the slot or releasing the ferrule end.
4. 4

   Access heater box area
   From the driver's side footwell area with lower panel removed, locate the heater box assembly mounted against the firewall. Use a flashlight to illuminate the area. The blend door control arm is located on the heater box; note its exact position before disconnecting, as access on the 1966 Corvette is tight.
5. 5

   Disconnect cable at blend door actuator
   Reach up toward the heater box and locate where the cable attaches to the blend door actuator arm. The actuator arm is a metal lever protruding from the side of the heater box. Use needle nose pliers to release the cable end from the actuator arm by compressing any retaining clip or sliding the cable end fitting out of the lever slot.
6. 6

   Remove cable housing from firewall grommet
   Trace the cable housing back to where it passes through a grommet in the firewall or heater box mounting. Work the cable housing out of the grommet by carefully pulling from inside the vehicle. If the grommet is hardened or stuck, carefully use a flat blade screwdriver to help pry it loose without damaging the grommet.
7. 7

   Remove old cable completely
   Once both ends are disconnected and the cable is free from the firewall grommet, carefully route the cable out from behind the dash. Note the exact routing path for installation of the new cable. Inspect all mounting points and clips for damage or wear.
8. 8

   Prepare new cable and lubricate
   Unpack the new heater control cable. If equipped, apply a small amount of white lithium grease to the inner cable wire where it slides within the housing. Do not over-lubricate as excess grease may attract dirt. Ensure the cable moves freely through its full range of motion before installation.
9. 9

   Route new cable through firewall
   Working from inside the vehicle, route the new cable housing through the same path as the original cable. Feed it through the firewall grommet from the inside, ensuring the grommet seats properly. The cable should pass through with minimal bending or kinking.
10. 10

    Connect cable to blend door actuator
    Reach up to the heater box and connect the cable end to the blend door actuator arm. Insert the cable end fitting into the lever slot and ensure it is fully seated. If equipped with a retaining clip, install it to secure the cable end. Verify the actuator arm moves freely through its full range when the cable is pulled and released.
11. 11

    Connect cable to control panel
    At the dash control panel, route the cable housing into the mounting bracket and install the retaining clip to secure it. Connect the inner cable wire to the temperature control lever by inserting the ferrule end into the lever slot or hooking it as designed. Ensure positive engagement.
12. 12

    Adjust cable operation
    With the cable connected at both ends, test the temperature control lever operation. Move the lever from full cold to full hot position. The blend door actuator arm should move through its complete range of travel. If the cable is too tight or loose, adjust by repositioning the cable housing in the dash mounting bracket before fully securing the retaining clip.

Reassembly

1. Reinstall the heater control panel trim bezel and secure with the 2 screws
2. Reinstall the lower dash panel and secure with the 4 Phillips head screws
3. Reconnect the negative battery cable
4. Replace floor mat and remove protective coverings from interior

Verification

• Start the engine and allow it to reach operating temperature
• Move the temperature control lever from full cold to full hot while monitoring airflow temperature
• Verify smooth operation with no binding or sticking throughout the lever's range
• Confirm that air temperature transitions properly from cold to hot in response to lever position
• Check that the control lever remains in position without drifting after adjustment
• Inspect all reinstalled panels for proper fit and secure attachment

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