Chrysler Full-Size Trucks 1967-1988 Repair Guide

Heater Core

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In order to prevent heater core freeze-up during A/C operation, it is necessary to maintain permanent type antifreeze protection of to 15°F (-9°C), or lower. A reading of -15°F (-26°C) is ideal since this protection also supplies sufficient corrosion inhibitors for the protection of the engine cooling system.

The same antifreeze should not be used longer than the manufacturer specifies.

REMOVAL & INSTALLATION




CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

1967-72 Models
WITHOUT AIR CONDITIONING

See Figures 1 and 2

  1. Disconnect battery ground cable.
  2.  
  3. Drain the radiator.
  4.  
  5. Disconnect the blower motor resistor and ground wires from the heater.
  6.  
  7. Disconnect and plug the heater core hoses.
  8.  

Make sure you have an ample supply of rags for any accidental coolant spills. Keep them within reach while removing and installing the heater core.

  1. Disconnect the control cables and underdash braces.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: Control assembly with cable connections-1968-72 models

  1. From the engine compartment, remove the 3 heater mounting nuts or bolts.
  2.  
  3. Lower the heater assembly to the floor of the truck, then remove the defroster hoses and air intake duct.
  4.  
  5. Remove the heater from the truck.
  6.  
  7. Remove the retaining nuts and lift the blower assembly out of the housing.
  8.  
  9. Remove the cover retaining nuts and lift the cover off the housing.
  10.  
  11. Remove the core retaining screws and lift the core out of the housing.
  12.  



Click image to see an enlarged view

Fig. Fig. 2: Heater unit assembly overview

  1. Installation is the reverse of removal.
  2.  
  3. Connect the battery ground cable, then fill the cooling system.
  4.  
  5. Let the engine warm up with the heater on, then check the coolant level.
  6.  

WITH AIR CONDITIONING

See Figure 3

  1. Using an approved R-12 recovery/recycling station, follow the manufacturer's instructions to discharge the refrigerant. See General Information & Maintenance .
  2.  

Be sure to consult the laws in your area before servicing the air conditioning system. In some states, it is ILLEGAL to perform repairs involving refrigerant unless the work is done by a certified technician.

  1. Disconnect the battery ground cable.
  2.  
  3. Drain the cooling system.
  4.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Disconnect the heater hoses at the core tubes. Plug the tubes.
  2.  

Make sure you have an ample supply of rags for any accidental coolant spills. Keep them within reach while removing and installing the heater core.

  1. Disconnect the refrigerant lines at the evaporator. Use a back-up wrench on each fitting. Cap all openings.
  2.  
  3. Disconnect the vacuum hoses, one from the intake manifold and two from the water valve. Push the hoses into the passenger compartment.
  4.  
  5. Remove the nuts from the mounting studs on the face of the firewall.
  6.  



Click image to see an enlarged view

Fig. Fig. 3: These common air conditioning vacuum and electrical circuits are concealed behind the dashboard

  1. From inside, remove the glove box and disconnect the actuator vacuum hose cluster from the back of the control switch.
  2.  
  3. Disconnect the control cables.
  4.  
  5. Detach all the electrical connectors.
  6.  
  7. Remove the ashtray, left cooler duct and defroster ducts at the left side of the housing.
  8.  
  9. Disconnect the support bracket from the left side of the housing.
  10.  
  11. Remove the 3 retaining screws from the face of the housing and remove the appearance shield. Collapse the distribution duct towards the back of the instrument panel.
  12.  
  13. Remove both windshield wiper arms.
  14.  
  15. Remove the 7 sheet metal screws and lift off the air intake grille from in front of the windshield.
  16.  
  17. Remove the 2 bolts from the support bracket at the back of the blower motor housing.
  18.  
  19. Pull the unit towards the rear of the cab until all studs are clear of the dash panel, then move the unit to the right and tilt it down and out from under the instrument panel.
  20.  
  21. Place the assembly on a clean work surface and remove the front cover.
  22.  
  23. Carefully pull the sensing tube out from the left side of the evaporator.
  24.  
  25. Remove the 11 retaining screws from the top of the housing and lift the cover plate off the housing.
  26.  
  27. Remove one retaining screw under the foam insulator at the core tubes and carefully lift the evaporator out of the housing.
  28.  
  29. Lift out the heater core.
  30.  

To install:
  1. Replace all sealing material.
  2.  
  3. Install the heater core.
  4.  
  5. Carefully lower the evaporator into the housing. Install one retaining screw under the foam insulator at the core tubes.
  6.  
  7. Install the cover plate and 11 retaining screws from the top of the housing.
  8.  
  9. Carefully install the sensing tube in the left side of the evaporator.
  10.  
  11. Install the front cover.
  12.  
  13. Position in the cab and on the studs.
  14.  
  15. Install the 2 bolts on the support bracket at the back of the blower motor housing.
  16.  
  17. Install the air intake grille from in front of the windshield. Install the 7 sheet metal screws
  18.  
  19. Install both windshield wiper arms.
  20.  
  21. Install the distribution duct. Install the appearance shield.
  22.  
  23. Connect the support bracket at the left side of the housing.
  24.  
  25. Install the ashtray and left cooler duct and the defroster ducts at the left side of the housing.
  26.  
  27. Connect all electrical connectors.
  28.  
  29. Connect the control cables.
  30.  
  31. From inside, connect the actuator vacuum hose cluster from the back of the control switch and install the glove box.
  32.  
  33. Install the nuts on the mounting studs on the face of the firewall.
  34.  
  35. Connect the vacuum hoses, one at the intake manifold and two at the water valve.
  36.  
  37. Connect the refrigerant lines at the evaporator. Use a back-up wrench on each fitting.
  38.  
  39. Connect the heater hoses at the core tubes.
  40.  
  41. Connect the battery ground cable.
  42.  
  43. Fill the cooling system.
  44.  
  45. Using an approved R-12 recovery/recycling station, follow the manufacturer's instructions to charge the refrigerant system. See General Information & Maintenance .
  46.  

1973-80 Models
WITHOUT AIR CONDITIONING

See Figure 4

  1. Disconnect the battery ground cable.
  2.  
  3. Drain the cooling system.
  4.  
  5. Disconnect the heater hoses at the core tubes. Plug the core tubes.
  6.  

Make sure you have an ample supply of rags for any accidental coolant spills. Keep them within reach while removing and installing the heater core.

  1. Disconnect the wiring.
  2.  
  3. Disconnect the control cables.
  4.  
  5. Disconnect the defroster ducts.
  6.  
  7. Disconnect the ground wire and cooling tube from the blower motor in the engine compartment.
  8.  
  9. Remove the bracket from the right side of the instrument panel and pull the panel rearward.
  10.  
  11. Remove the 7 mounting nuts from the engine side of the firewall and one from the inside at the right kick panel.
  12.  



Click image to see an enlarged view

Fig. Fig. 4: Exploded view of heater housing components

  1. Pull the heater assembly out of the vehicle.
  2.  
  3. Remove the heater core cover.
  4.  
  5. Unfasten and remove the screws fastening the heater core to the bottom of the heater housing.
  6.  
  7. Lift out the heater core.
  8.  

To install:
  1. Place the core in the housing and fasten.
  2.  
  3. Position the blend air door and right vent door in the housing, then fasten the heater core cover to the heater housing.
  4.  
  5. Install the heater assembly as described in reverse order. Be sure to adjust the cables.
  6.  
  7. Connect the battery ground cable, then fill the cooling system.
  8.  

WITH AIR CONDITIONING

See Figure 5

  1. Disconnect the battery ground cable.
  2.  
  3. Drain the cooling system.
  4.  
  5. Disconnect the heater hoses at the firewall.
  6.  
  7. Remove the glove box and ashtray.
  8.  
  9. Remove the right and left air conditioning ducts.
  10.  
  11. Remove the distribution duct.
  12.  
  13. Remove the center air outlet and duct.
  14.  



Click image to see an enlarged view

Fig. Fig. 5: Heater assembly and related components-1973-80 models

  1. Disconnect the wiring harness from the resistor.
  2.  
  3. Disconnect the vacuum lines from the rear housing.
  4.  
  5. Remove the 22 screws from the rear housing.
  6.  
  7. Remove the 2 plugs and, using a long extension, remove the 2 screws from inside the housing.
  8.  
  9. While holding the defroster door in the HEAT position, separate the unit.
  10.  
  11. Remove 1 screw from the engine side of the firewall and 2 screws from each end of the core, then slide out the core.
  12.  

Make sure you have an ample supply of rags for any accidental coolant spills. Keep them within reach while removing and installing the heater core.

To install:
  1. Slide the core into place, then install one screw in the engine side of the firewall and two screws in each end of the core.
  2.  
  3. While holding the defroster door in the HEAT position, secure the unit.
  4.  
  5. Using a long extension, install the 2 screws inside the housing. Install the 2 plugs.
  6.  
  7. Install the 22 screws in the rear housing.
  8.  
  9. Connect the vacuum lines at the rear housing.
  10.  
  11. Connect the wiring harness at the resistor.
  12.  
  13. Install the center air outlet and duct.
  14.  
  15. Install the distribution duct.
  16.  
  17. Install the right and left air conditioning ducts.
  18.  
  19. Install the glove box and ashtray.
  20.  
  21. Connect the heater hoses at the firewall.
  22.  
  23. Connect the battery ground cable.
  24.  
  25. Fill the cooling system.
  26.  

1981-88 Models
WITH STANDARD HEATER AND NO AIR CONDITIONING
  1. Disconnect the battery ground cable.
  2.  
  3. Drain the cooling system.
  4.  
  5. Disconnect the heater hoses at the core tubes. Plug the tubes.
  6.  

Make sure you have an ample supply of rags for any accidental coolant spills. Keep them within reach while removing and installing the heater core.

  1. Remove the right cowl side trim panel, if equipped.
  2.  
  3. Remove the glove box by removing the 4 screws at the base and swinging out from the bottom to avoid catch and stops.
  4.  
  5. Working through the glove box opening, remove the support brace.
  6.  
  7. Remove the 8 screws from the right side of the instrument panel lower reinforcement. Disconnect the ground strap.
  8.  
  9. Disconnect the control cables.
  10.  
  11. Disconnect the blower motor wires.
  12.  
  13. Disconnect the wiring at the resistor block.
  14.  
  15. Remove the heater unit retaining screw from the cowl side sheet metal.
  16.  
  17. Remove the 6 mounting nuts from the engine side of the firewall.
  18.  
  19. Take out the heater unit, then remove its cover and lift out the core.
  20.  

To install:
  1. Insert the core and install the cover, then position the heater unit.
  2.  
  3. Install the 6 mounting nuts on the engine side of the firewall.
  4.  
  5. Install the heater unit retaining screw at the cowl side sheet metal.
  6.  
  7. Connect the wiring at the resistor block.
  8.  
  9. Connect the blower motor wires.
  10.  
  11. Connect the control cables.
  12.  
  13. Install the 8 screws at the right side of the instrument panel lower reinforcement. Connect the ground strap.
  14.  
  15. Working through the glove box opening, install the support brace.
  16.  
  17. Install the glove box.
  18.  
  19. Install the right cowl side trim panel, if equipped.
  20.  
  21. Connect the heater hoses at the core tubes.
  22.  
  23. Connect the battery ground cable.
  24.  
  25. Fill the cooling system.
  26.  

WITH BI-LEVEL HEATER AND NO AIR CONDITIONING
  1. Disconnect the battery ground cable.
  2.  
  3. Drain the cooling system.
  4.  
  5. Disconnect the heater hoses at the core tubes. Plug the tubes.
  6.  

Make sure you have an ample supply of rags for any accidental coolant spills. Keep them within reach while removing and installing the heater core.

  1. Remove the drain tube.
  2.  
  3. Position the gearshift and transfer case levers away from the instrument panel.
  4.  
  5. Remove the glove box.
  6.  
  7. Working through the glove box opening, remove the support brace.
  8.  
  9. Remove the ashtray.
  10.  
  11. Remove the 8 screws from the right side of the instrument panel lower reinforcement. Disconnect the ground strap.
  12.  
  13. Remove the center distribution duct.
  14.  
  15. Disconnect the control cables.
  16.  
  17. Disconnect the vacuum lines.
  18.  
  19. Disconnect the blower motor wires.
  20.  
  21. Disconnect the wiring at the resistor block.
  22.  
  23. Pull the carpet back and make sure that the grommet is free from the firewall.
  24.  
  25. Remove the heater unit retaining screw from the cowl side sheet metal.
  26.  
  27. Remove the 7 mounting nuts from the engine side of the firewall.
  28.  
  29. Remove the heater unit. You may have to slightly bend the plastic instrument panel trim for clearance.
  30.  
  31. Remove the 10 screws and 3 door cranks, then separate the cover from the housing.
  32.  
  33. Carefully slide out the core.
  34.  

To install:
  1. Install the core, then assemble its housing.
  2.  
  3. Install the 7 mounting nuts on the engine side of the firewall.
  4.  
  5. Install the heater unit retaining screw at the cowl side sheet metal.
  6.  
  7. Install and align the carpet.
  8.  
  9. Connect the vacuum lines on engine side, and make sure the grommet is seated in dash panel.
  10.  
  11. Connect the wiring at the resistor block.
  12.  
  13. Connect the blower motor wires.
  14.  
  15. Connect the control cables.
  16.  
  17. Install the 8 screws at the right side of the instrument panel lower reinforcement. Connect the ground strap.
  18.  
  19. Working through the glove box opening, install the support brace.
  20.  
  21. Install the center distribution duct.
  22.  
  23. Install the glove box.
  24.  
  25. Install the ashtray.
  26.  
  27. Connect the heater hoses at the core tubes.
  28.  
  29. Connect the battery ground cable.
  30.  
  31. Fill the cooling system.
  32.  

WITH AIR CONDITIONING

See Figures 6 and 7

  1. Using an approved R-12 recovery/recycling station, follow the manufacturer's instructions to discharge the refrigerant system. See General Information & Maintenance .
  2.  
  3. Disconnect the battery ground cable.
  4.  
  5. Drain the cooling system.
  6.  
  7. Disconnect the refrigerant lines at the evaporator and the heater hoses at the core tubes. Always use a back-up wrench on the A/C fittings. Plug the all openings at once!.
  8.  
  9. Remove the drain tube.
  10.  
  11. Position the gearshift and transfer case levers away from the instrument panel.
  12.  
  13. Remove the glove box.
  14.  
  15. Working through the glove box opening, remove the support brace.
  16.  
  17. Remove the ashtray.
  18.  
  19. Remove the 8 screws from the right side of the instrument panel lower reinforcement. Disconnect the ground strap.
  20.  
  21. Remove the center distribution duct.
  22.  
  23. Disconnect the control cables.
  24.  
  25. Detach the vacuum lines.
  26.  
  27. Disconnect the blower motor wires.
  28.  



Click image to see an enlarged view

Fig. Fig. 6: Heater assembly and related components-1981-85 models



Click image to see an enlarged view

Fig. Fig. 7: Heater assembly and related components-1986-88 models

  1. Detach the wiring at the resistor block.
  2.  
  3. Pull the carpet back and make sure the grommet is free from the firewall.
  4.  
  5. Remove the heater unit retaining screw from the cowl side sheet metal.
  6.  
  7. Remove the 7 mounting nuts from the engine side of the firewall.
  8.  
  9. Remove the heater unit. You may have to slightly bend the plastic instrument panel trim for clearance.
  10.  
  11. Remove the 10 screws and 3 door cranks, then separate the cover from the housing.
  12.  
  13. Carefully slide out the core.
  14.  

To install:
  1. Insert the heater core, then assemble its housing.
  2.  
  3. Properly position the heater unit to the vehicle.
  4.  
  5. Install the 7 mounting nuts on the engine side of the firewall.
  6.  
  7. Install the heater unit retaining screw at the cowl side sheet metal.
  8.  
  9. Connect the wiring at the resistor block.
  10.  
  11. Attach the blower motor wires.
  12.  
  13. Connect the control cables.
  14.  
  15. Install the 8 screws at the right side of the instrument panel lower reinforcement. Connect the ground strap.
  16.  
  17. Working through the glove box opening, install the support brace.
  18.  
  19. Install the center distribution duct.
  20.  
  21. Install the glove box.
  22.  
  23. Install the ashtray.
  24.  
  25. Connect the refrigerant hoses at the evaporator. Always use new O-rings coated with clean refrigerant oil. Always use a back-up wrench on the fittings. Attach the heater hoses at the core tubes.
  26.  
  27. Connect the battery ground cable.
  28.  
  29. Fill the cooling system.
  30.  
  31. Using an approved R-12 recovery/recycling station, follow the manufacturer's instructions to evacuate and charge the refrigerant system.
  32.  

 
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