Heater Control Valve

Procedure to remove and replace the heater control valve on a 2005 Dodge Viper with 8.3L V10 engine, including coolant draining and hose management.

Warnings

Tools required

Parts

• Heater control valve × 1 — Use OEM specification
• Hose clamps (if reusing originals shows wear) × 2 — Use OEM specification

Fluids

• Zerex G-05 HOAT 50/50 coolant — 2 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level surface and engage parking brake
3. Place drain pan under radiator drain cock
4. Open hood and secure in raised position

Procedure

1. 1

   Drain Cooling System
   Open the radiator drain cock at the bottom of the radiator and drain enough coolant to drop the level below the heater control valve into the drain pan. You do not need to drain the entire system, only enough to drop the coolant level below the heater control valve. Close the drain cock once coolant flow stops or slows to a drip.
2. 2

   Locate Heater Control Valve
   The heater control valve is mounted on the passenger side firewall, connected to two heater hoses. It is positioned between the engine and the firewall, typically secured with a mounting bracket. Trace the heater hoses from the engine forward to locate the valve assembly.
3. 3

   Disconnect Vacuum Line
   Locate the vacuum control line connected to the heater control valve actuator (if equipped with vacuum-operated valve). Carefully pull the vacuum line straight off the valve nipple. Inspect the line for cracks or damage and replace if necessary.
4. 4

   Loosen Inlet Hose Clamp
   Using hose clamp pliers or a flathead screwdriver, loosen the hose clamp securing the inlet heater hose (from engine) to the heater control valve. Slide the clamp back along the hose approximately 2-3 inches away from the valve connection point. Expect residual coolant to drain when the hose is removed.
5. 5

   Remove Inlet Hose
   Twist the inlet hose gently while pulling to break the seal, then remove it from the heater control valve inlet fitting. Have shop towels ready to catch residual coolant. Direct the hose end upward or plug it temporarily to minimize additional coolant loss.
6. 6

   Loosen Outlet Hose Clamp
   Loosen the hose clamp on the outlet heater hose (going to heater core) using the same method as the inlet. Slide the clamp back along the hose away from the valve.
7. 7

   Remove Outlet Hose
   Twist and pull the outlet hose from the heater control valve outlet fitting. Catch any remaining coolant with shop towels. Position the hose end upward to prevent further drainage.
8. 8

   Remove Valve Mounting Hardware
   Remove the 2 mounting bolts securing the heater control valve bracket to the firewall. These are typically 8mm or 10mm bolts. Keep the mounting bracket attached to the valve for easier reinstallation alignment.
   Torque spec

   Valve Mounting8 Nm (6 lb-ft)
9. 9

   Remove Heater Control Valve
   Carefully extract the heater control valve assembly with mounting bracket from the engine bay. Work it through the available space between engine components and firewall. Inspect the old valve for signs of leakage, corrosion, or mechanical failure.
10. 10

    Install New Heater Control Valve
    Position the new heater control valve with mounting bracket into the firewall location. Align the mounting holes with the firewall mounting points. If the bracket was removed from the valve, ensure it is attached to the new valve before installation.
11. 11

    Secure Valve Mounting Hardware
    Install the 2 mounting bolts through the bracket into the firewall. Hand-tighten first to ensure proper alignment, then torque to specification using a torque wrench.
    Torque spec

    Valve Mounting8 Nm (6 lb-ft)
12. 12

    Connect Outlet Hose
    Push the outlet heater hose (to heater core) firmly onto the valve outlet fitting until it seats completely against the fitting shoulder. Slide the hose clamp into position approximately 1/4 inch from the end of the fitting and tighten securely.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
13. 13

    Connect Inlet Hose
    Push the inlet heater hose (from engine) firmly onto the valve inlet fitting until fully seated. Position the hose clamp and tighten to specification.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
14. 14

    Reconnect Vacuum Line
    Push the vacuum control line firmly onto the valve actuator nipple until it seats completely. Tug gently to verify secure connection.
15. 15

    Refill Cooling System
    Using a coolant funnel at the specified cooling system fill/degas point, add Zerex G-05 HOAT 50/50 coolant to replace the amount drained. Fill slowly to allow air to escape, then add coolant to the overflow/degas reservoir to the FULL COLD mark.
16. 16

    Bleed Air from System
    With the radiator cap still off, start the engine and allow it to idle. Turn the heater controls to maximum heat and fan speed. Watch the coolant level in the radiator and add coolant as the level drops while air purges from the system. Allow the engine to reach operating temperature (thermostat opens). Squeeze the upper radiator hose several times to help purge trapped air.
17. 17

    Final Fill and Cap Installation
    Once the engine reaches operating temperature and no more air bubbles emerge from the radiator, top off coolant to the radiator neck. Install the radiator cap securely. Check the overflow reservoir level and adjust to the FULL HOT mark if necessary.

Reassembly

1. Reassembly is completed during the installation steps above
2. Ensure all hose clamps are tightened to specification to prevent coolant leaks
3. Verify vacuum line connection is secure to ensure proper valve operation

Verification

• Run engine to full operating temperature and verify no coolant leaks at valve connections
• Test heater function by setting climate control to maximum heat and verifying hot air output
• Check coolant level in overflow reservoir after engine cools completely and top off if necessary
• Inspect the heater control valve area for any signs of coolant drips or seepage after a test drive
• Verify vacuum line connection (if equipped) by listening for vacuum leaks at idle

Related trouble codes on this vehicle

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

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle