Chevrolet Blazer/Jimmy 1969-1982 Repair Guide

Heater Core

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REMOVAL & INSTALLATION



1969-72 Models
WITHOUT AIR CONDITIONING


Click image to see an enlarged view

Fig. Fig. 1 Sectional views of the heater controls-1969-72 models


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

  1. Drain the cooling system and disconnect the battery.
  2.  
  3. Remove the electrical connection at the blower.
  4.  
  5. Remove the heater hoses at the core tubes.
  6.  
  7. Loosen and move the right front fender skirt. Remove enough screws so that the skirt can be moved outward.
  8.  
  9. Working from under the dash, remove the seal on the temperature door cable and disconnect the cable from the temperature door.
  10.  
  11. Pull the case away from the mounting studs after removing the retaining bolts and nuts.
  12.  
  13. Remove the core retainers and remove the core.
  14.  
  15. Installation is the reverse of removal.
  16.  

1969-72 Models
WITH FACTORY INSTALLED AIR CONDITIONING

Models with dealer installed air conditioning use the same procedure as those without air conditioning.


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

  1. Drain the coolant. Disconnect the battery ground cable.
  2.  
  3. Detach the heater hoses from the core tubes at the firewall.
  4.  
  5. Remove the stud nuts on the engine side of the firewall.
  6.  
  7. Remove the glove box.
  8.  
  9. Unplug the relay connector and remove the right ball outlet hose.
  10.  
  11. Remove the screw holding the panel outlet air distributor to the heater case. Remove the heater case retaining screws.
  12.  
  13. Pull the heater case away from the firewall; reach in and disconnect the resistor connector. Remove the resistor harness grommet and remove the harness.
  14.  
  15. Remove the heater case. Remove the core mounting straps.
  16.  
  17. Installation is the reverse of removal.
  18.  

1973-82 Models
WITHOUT AIR CONDITIONING


Click image to see an enlarged view

Fig. Fig. 2 Heater distribution duct-1973-80 models without A/C


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

  1. Disconnect the battery ground cable.
  2.  
  3. Disconnect the heater hoses at the core tubes and drain the coolant into a clean container. The coolant may be used again if it is still clean. Plug the core tubes to prevent any excess spillage.
  4.  
  5. Remove the nuts from the distributor duct studs in the engine compartment.
  6.  
  7. Remove the glove compartment and door.
  8.  
  9. Disconnect the "Air-Defrost" and "Temperature" door cables.
  10.  
  11. Remove the floor outlet and remove the defroster duct-to-heater distributor screw.
  12.  
  13. Remove the heater distributor-to-dash panel screws. Pull the assembly rearward to gain access to the wiring harness and disconnect the wires attached to the unit.
  14.  
  15. Remove the heater unit from the truck.
  16.  
  17. Remove the heater core retaining straps and remove the core from the truck.
  18.  
  19. Installation is the reverse of removal. Be sure that the core-to-case and case-to-dash panel sealer is intact. Fill the cooling system and check for leaks.
  20.  

1973-82 Models
WITH AIR CONDITIONING

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

  1. Disconnect the battery ground cable.
  2.  
  3. Drain the coolant.
  4.  
  5. Remove the heater hoses from the core tubes. Plug the tubes to prevent spillage.
  6.  
  7. Remove the glove box and door.
  8.  
  9. Remove the screws holding the center duct to the selector duct and to the instrument panel. Remove the center upper and lower ducts.
  10.  
  11. Disconnect the control cable at the temperature door.
  12.  
  13. Remove the three stud nuts from the firewall. Remove the selector duct to firewall screw inside the truck.
  14.  
  15. Pull the selector duct assembly back until the core tubes clear the firewall, then lower it to disconnect the vacuum and electrical connections.
  16.  
  17. Disconnect the vacuum and electrical harness.
  18.  
  19. Remove the selector duct assembly and remove the core mounting straps.
  20.  
  21. Remove the heater core.
  22.  
  23. Installation is the reverse of removal.
  24.  

 
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