Heater Control Valve

This procedure covers the removal and replacement of the heater control valve on a 2007 Ram 3500 with the 5.9L Cummins diesel engine and 4WD.

Warnings

Tools required

Parts

• Heater control valve × 1 — Use OEM specification
• Heater hose clamps (if reusing old clamps is not possible) × 2 — Worm-gear type or OEM spring clamps

Fluids

• HOAT coolant 50/50 — 2 qt

Preparation

1. Ensure engine is completely cool to the touch (minimum 2 hours after last operation)
2. Park vehicle on level ground and engage parking brake
3. Place drain pan under radiator drain cock
4. Open hood and secure in upright position
5. Remove engine cover by lifting upward (friction fit)
6. Locate heater control valve on passenger side of engine bay near firewall, inline with heater hoses

Procedure

1. 1

   Drain cooling system
   Open the radiator drain cock at the bottom driver side of the radiator to drain approximately 2-3 gallons of coolant into the drain pan. You do not need to drain the entire system, just enough to lower the coolant level below the heater control valve. Once coolant flow slows significantly, close the drain cock.
2. 2

   Disconnect negative battery cable
   Disconnect the negative battery cable(s) from the battery to prevent any electrical shorts. Note that this Cummins application uses dual batteries; disconnect the negative terminal(s) as required. Use a 10mm wrench or socket to loosen the negative terminal clamp. Use a 10mm wrench or socket to loosen the negative terminal clamp.
3. 3

   Disconnect electrical connector
   Locate the electrical connector on the heater control valve body. Press the locking tab and pull the connector straight off the valve. Be gentle as the connector can be brittle after years of heat cycling.
4. 4

   Remove inlet hose
   Using hose clamp pliers or a flat-blade screwdriver, loosen or remove the hose clamp on the inlet side (side closest to engine) of the heater control valve. Twist the hose gently to break it free from the valve nipple, then pull it off. Be prepared for residual coolant to drain from the hose. Have shop towels ready to catch spillage.
5. 5

   Remove outlet hose
   Using hose clamp pliers or a flat-blade screwdriver, loosen or remove the hose clamp on the outlet side (side going toward heater core/firewall) of the heater control valve. Twist the hose gently to break it free from the valve nipple, then pull it off. Again, be prepared for residual coolant drainage.
6. 6

   Remove mounting hardware
   The heater control valve is typically mounted to a bracket with a single bolt or clip. Remove the mounting bolt (typically 8mm or 10mm) or release the mounting clip to free the valve from its bracket. Note the orientation and routing of the valve for reinstallation.
7. 7

   Remove heater control valve
   Pull the heater control valve away from the mounting bracket and out of the engine bay. Inspect the hose connections for damage, cracks, or hardening. If hoses show signs of deterioration, consider replacing them as well.
8. 8

   Install new heater control valve
   Position the new heater control valve in the mounting bracket in the same orientation as the old valve. Ensure the inlet port (typically marked or comes from the engine side) is oriented correctly. Secure the valve to the mounting bracket with the bolt or clip.
9. 9

   Connect inlet hose
   Slide the inlet hose onto the inlet nipple of the new heater control valve, pushing it firmly until it bottoms out on the nipple. Position a new hose clamp (or reuse the original if in good condition) over the hose connection and tighten securely. Ensure the clamp is positioned beyond the bead on the nipple.
10. 10

    Connect outlet hose
    Slide the outlet hose onto the outlet nipple of the new heater control valve, pushing it firmly until it bottoms out on the nipple. Position a new hose clamp (or reuse the original if in good condition) over the hose connection and tighten securely. Ensure the clamp is positioned beyond the bead on the nipple.
11. 11

    Reconnect electrical connector
    Push the electrical connector onto the heater control valve until you hear or feel it click into place. Tug gently on the connector to verify it is locked securely.
12. 12

    Refill cooling system
    Reconnect the negative battery cable. Add HOAT 50/50 coolant to the radiator and overflow reservoir to bring the system back to proper level. Add coolant to match the amount drained (approximately 2-3 gallons) and adjust as needed. Fill the radiator to the top and the overflow reservoir to the FULL COLD mark.
13. 13

    Bleed cooling system
    Start the engine and allow it to idle with the radiator cap OFF. Turn the heater to maximum heat and fan speed. As the engine warms and the thermostat opens, you will see the coolant level drop in the radiator. Continue adding coolant to maintain level. Watch for air bubbles to stop and coolant to circulate smoothly. Once the upper radiator hose becomes hot and no more air bubbles appear, the system is bled. Turn off engine and allow to cool.

Reassembly

1. Once engine is cool, top off radiator and overflow reservoir as needed
2. Reinstall engine cover by aligning tabs and pressing down firmly
3. Double-check all hose connections for tightness and proper clamp positioning
4. Verify electrical connector is fully seated and locked

Verification

• Start the engine and verify no coolant leaks at heater control valve connections
• Allow engine to reach operating temperature and verify heater produces hot air when climate controls are set to heat
• Check for proper heater temperature control by adjusting temperature settings from cold to hot
• After initial test drive, recheck coolant level when engine is cool and top off if necessary
• Monitor for leaks and proper heater operation over the next few days

Related trouble codes on this vehicle

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