Heater Core

This procedure covers removal and replacement of the heater core in a 2007 Ram 3500 with 5.9L Cummins diesel engine, requiring dashboard disassembly and coolant system drainage.

Warnings

Tools required

Parts

• Heater core × 1 — Use OEM specification
• Heater core inlet/outlet O-rings × 2 — Use OEM specification
• HVAC foam seals × 1 — Use OEM specification
• Dashboard retaining clips (assorted) × 10 — Replacement for broken clips

Fluids

• HOAT coolant 50/50 — 28 qt

Preparation

1. Park vehicle on level surface and allow engine to cool completely (minimum 3 hours)
2. Disconnect both negative and positive battery cables, wait 10 minutes for airbag system capacitor discharge
3. Place protective covers over front seats and floor carpeting
4. Remove driver and passenger floor mats
5. Position large drain pan under radiator petcock on passenger side of radiator
6. Take photos of dashboard connections and wiring routing for reassembly reference

Procedure

1. 1

   Drain cooling system
   Open radiator petcock on passenger side lower corner of radiator. Remove radiator cap to allow complete drainage. Draining the radiator is sufficient for this job. If more complete drainage is desired, the 5.9L Cummins has a single block coolant drain on the side of the engine block; opening it is optional for a heater core replacement. Collect coolant in appropriate container. Once drained, close all drain points.
2. 2

   Remove lower dashboard panels and covers
   Remove lower steering column cover by removing two screws at bottom and releasing clips at top. Remove lower instrument panel cover on passenger side (pull firmly to release clips). Remove driver side knee bolster panel by removing four screws. Disconnect any electrical connectors for lights or switches as panels are removed.
3. 3

   Remove center console and floor components
   Remove floor console if equipped: remove cup holder insert, remove screws hidden beneath, disconnect power outlet and shift boot connections. Remove center HVAC duct by releasing clips at registers. Remove floor air distribution ducts on both driver and passenger sides by releasing mounting tabs.
4. 4

   Disconnect instrument cluster and steering column
   Remove instrument cluster bezel by releasing retaining clips. Remove four screws securing instrument cluster, pull cluster forward and disconnect electrical connectors and PRNDL cable if equipped with automatic transmission. Lower steering column by removing the nuts securing the column bracket to the support (verify count and size against factory service documentation). Allow column to rest on driver seat with protective covering.
5. 5

   Remove center stack and radio assembly
   Remove radio/climate control bezel by releasing clips around perimeter. Remove screws securing radio and climate control unit. Disconnect electrical connectors, antenna cable, and vacuum lines from climate control unit. Mark vacuum line positions with tape for correct reinstallation.
6. 6

   Disconnect heater hoses at firewall
   From engine compartment, locate heater hoses on passenger side firewall. Place drain pan underneath connections. Use pliers to release spring clamps or loosen worm-drive clamps on both inlet and outlet heater hoses. Remove hoses from heater core tubes and cap openings with plugs or tape to prevent debris entry.
   ⚠Residual coolant will drain from hoses and heater core. Have rags and drain pan ready.
7. 7

   Remove upper dashboard mounting and supports
   Locate and remove dashboard mounting bolts: typically two bolts at each A-pillar (behind end caps), two bolts at center support bracket, and multiple bolts along upper dashboard edge. Remove any ground wire connections. Pull dashboard rearward approximately 6 inches to access HVAC housing - dashboard does not need complete removal on most Ram 3500 applications.
8. 8

   Access and remove HVAC housing components
   With dashboard pulled back, locate HVAC housing on passenger side. Remove blower motor assembly (three screws) and set aside. Remove evaporator temperature sensor if blocking access. Locate HVAC housing cover held by multiple screws and clips - this cover provides access to heater core.
   ℹ️HVAC housing is bulky and difficult to access. Use work light to identify all fasteners before attempting removal.
9. 9

   Remove heater core retaining bracket and extract core
   Remove heater core retaining bracket (typically two screws at top). Note orientation of heater core and position of foam seals. Carefully slide heater core out of HVAC housing, tilting as necessary to clear housing opening. Residual coolant will drain - have rags ready. Inspect HVAC housing for debris, leaves, or corrosion.
10. 10

    Install new heater core
    Install new O-rings on heater core inlet and outlet tubes with light coating of coolant for lubrication. Install new foam seals in HVAC housing if deteriorated. Carefully slide new heater core into HVAC housing, ensuring tubes align with firewall openings. Install retaining bracket and secure with screws. Verify heater core is fully seated in housing.
11. 11

    Reassemble HVAC components and dashboard
    Reinstall HVAC housing cover with all screws and clips. Reinstall evaporator temperature sensor and blower motor assembly. Push dashboard forward into original position and install all mounting bolts at A-pillars, center support, and upper edge. Reconnect all ground wires. Reinstall instrument cluster, reconnect all electrical connectors and PRNDL cable.
12. 12

    Reconnect heater hoses and refill coolant system
    From engine compartment, connect heater hoses to heater core tubes and secure with clamps (spring clamps or worm-drive clamps). Ensure hoses are fully seated on tubes. With all drain points closed, refill cooling system with Mopar HOAT (G-05 equivalent) 50/50 coolant through radiator and overflow tank. Fill slowly to allow air to escape. Use vacuum fill tool if available to eliminate air pockets in Cummins cooling system.
    ⚠Cummins 5.9L diesel systems are prone to air pockets. Burping procedure is critical to prevent overheating.
13. 13

    Bleed cooling system and check for leaks
    Start engine and set heater to maximum temperature and fan speed. Allow engine to reach operating temperature (195-210°F) while monitoring coolant level. Add coolant as level drops during bleeding process. Squeeze upper radiator hose to help purge air. Run engine for 20 minutes, checking heater hose connections and heater core area for leaks. Shut off engine, allow to cool, and recheck coolant level.
    ⚠️Monitor engine temperature gauge continuously during bleeding process. Shut down immediately if temperature exceeds normal range to prevent engine damage.

Reassembly

1. Reinstall steering column bracket and torque mounting nuts to secure column
2. Reinstall center stack components: radio, climate control unit with vacuum lines in correct positions
3. Reinstall all dashboard trim panels, bezels, and covers - ensure all clips are fully seated
4. Reinstall floor console and air distribution ducts
5. Reconnect battery cables (positive first, then negative)
6. Reset clock and radio presets as needed

Verification

• Verify heater produces hot air at all blower speeds and temperature settings
• Check coolant level in overflow tank when engine is cold - should be at FULL COLD mark
• Inspect engine compartment heater hose connections for coolant leaks after test drive
• Verify no coolant smell or dampness in passenger floor area
• Check dashboard for squeaks or rattles and verify all trim panels are secure
• Monitor engine temperature during first few drives to ensure proper cooling system operation
• Check for diagnostic trouble codes related to airbag system after battery reconnection

Related trouble codes on this vehicle

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