GM Prizm/Nova 1985-1993 Repair Guide

Heater Core

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The heater core is simply a small heat exchanger (radiator) within the car. If the driver selects heat on the control panel, a water valve is opened allowing engine coolant to circulate through the heater core. The blower fan circulates air through the fins, picking up the heat from the engine coolant. The heated air is ducted into the car and the coolant is routed back to the engine. Moving the control to a cooler setting reduces the amount of hot water flowing into the core, thus reducing the amount of heat.

REMOVAL & INSTALLATION



1985-88
  1. Disconnect the negative battery cable and then drain the cooling system.
  2.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by the 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 hose from the core in the engine compartment.
  2.  
  3. Remove the 6 clips from the lower part of the heater case, then remove the lower part of the case.
  4.  
  5. Carefully pry open the lower part of the heater case.
  6.  
  7. Remove the core assembly from the heater case. Handle the core carefully and do not allow the fins to be crushed or deformed.
  8.  

To install:
  1. When reinstalling, position the core properly and install the lower part of the case.
  2.  
  3. Install the 6 clips, making sure each is properly secured.
  4.  
  5. Connect the heater hoses. Check them for any signs of weakness or fraying and use new clamps if necessary.
  6.  
  7. Refill the coolant to the proper level.
  8.  
  9. Connect the negative battery cable.
  10.  

1989-92

The heater case and core are located directly behind the center console. Access to the heater case requires removal of the entire console as well as most of the dashboard assembly. Please refer to the proper sub-topics for removal procedures. Instrument Cluster and Radio removal are explained later in this section. Instrument Panel and Console removal are found in Body & Trim . Steering Wheel removal and installation is discussed in Suspension & Steering .

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the steering wheel.
  4.  
  5. Remove the trim bezel from the instrument cluster.
  6.  
  7. Remove the cup holder from the console.
  8.  
  9. Remove the radio.
  10.  
  11. Remove the instrument panel (dashboard) assembly and the instrument cluster. Label and carefully disconnect all of the dash wiring harnesses. Remember to release the locking mechanism on each connector first.
  12.  
  13. Remove the center console and all the console trim. Work carefully and don't break the plastic pieces.
  14.  
  15. Remove the lower dash trim and the side window air deflectors.
  16.  
  17. Drain the coolant from the cooling system.
  18.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by the 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 control cables from the heater case. Don't lose any of the small clips.
  2.  
  3. Disconnect the ductwork from the heater case.
  4.  
  5. Disconnect the blower switch wiring harness and heater control assembly.
  6.  
  7. Remove the 2 center console support braces.
  8.  
  9. Loosen the clamps and remove the heater hoses from the case. Remove the grommet from the cowling.
  10.  
  11. Remove the mounting nuts and bolts holding the heater core and the air distribution case to the firewall.
  12.  
  13. Remove the heater case and air distribution case from the car as a unit.
  14.  
  15. Remove the screws and clips from the case halves and separate the case.
  16.  
  17. Remove the heater core from the case.
  18.  

To install:
  1. Install the heater core into the case, position the case halves and secure the retaining screws and clips.
  2.  
  3. Install the case assembly in the car and secure it with the mounting nuts and bolts.
  4.  
  5. Connect the heater hoses (use new clamps if necessary) and attach the grommet to the cowl.
  6.  
  7. Connect the air ducts to the case and connect the control cables.
  8.  
  9. Install the 2 center console support braces.
  10.  
  11. Install the blower wiring harness and the heater control assembly.
  12.  
  13. Place the dashboard in position within the car. When it is loosely in place, connect the wiring harness connectors, making sure each is firmly seated and the wiring properly secured.
  14.  
  15. Install the center console and its trim pieces.
  16.  
  17. Install the radio.
  18.  
  19. Install the cup holder.
  20.  
  21. Install the trim bezel around the instrument cluster.
  22.  
  23. Install the steering wheel.
  24.  
  25. Refill the coolant to the proper level.
  26.  
  27. Connect the negative battery cable.
  28.  

1993

See Figures 1 through 8

  1. Disconnect the negative battery cable.
  2.  
  3. If equipped with air conditioning, remove the evaporator case.
  4.  
  5. Drain the coolant from the cooling system.
  6.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by the 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 core inlet and outlet hoses.
  2.  
  3. Remove the heater core grommet from the vehicle.
  4.  
  5. Refer to Body & Trim and remove the instrument panel from the vehicle.
  6.  
  7. Remove the left side instrument panel brace from the vehicle by removing the 6 retaining bolts.
  8.  
  9. Remove the right side instrument panel brace from the vehicle by removing the 1 retaining bolt and nut.
  10.  
  11. Remove the center ventilation duct from the vehicle by removing the 2 retaining screws.
  12.  
  13. Disconnect the instrument panel left side ventilation duct.
  14.  
  15. Remove the case from the vehicle by removing the 4 retaining nuts.
  16.  
  17. Disconnect the heater core mounting brackets by removing the 2 retaining screws.
  18.  
  19. Slide the heater core out of the heater case.
  20.  

To install:
  1. Slide the heater core into the heater case and install the 2 retaining screws.
  2.  
  3. Install the case to the vehicle and tighten the 4 retaining nuts to 89 inch lbs. (10 Nm).
  4.  
  5. Connect the instrument panel left side ventilation duct.
  6.  
  7. Install the center ventilation duct to the vehicle and install the 2 retaining screws.
  8.  
  9. Install the right side instrument panel brace to the vehicle and tighten the 1 retaining bolt and nut to 18 ft. lbs. (25 Nm).
  10.  
  11. Install the left side instrument panel brace to the vehicle and tighten the 6 retaining bolts 18 ft. lbs. (25 Nm).
  12.  
  13. Refer to Body & Trim and install the instrument panel to the vehicle.
  14.  
  15. Install the heater core grommet to the vehicle.
  16.  
  17. Connect the heater core inlet and outlet hoses.
  18.  
  19. Fill the cooling system.
  20.  
  21. If equipped with air conditioning, install the evaporator case.
  22.  



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Fig. Fig. 1: Heater and ventilation system components - 1993 models



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Fig. Fig. 2: Instrument panel support beam - 1993 models



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Fig. Fig. 3: Blower motor case - 1993 models



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Fig. Fig. 4: Heater and ventilation ducts - 1993 models

  1. Connect the negative battery cable.
  2.  



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Fig. Fig. 5: Instrument panel center ventilation duct - 1993 models



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Fig. Fig. 6: Heater core hoses - 1993 models



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Fig. Fig. 7: Heater case - 1993 models



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Fig. Fig. 8: Heater core - 1993 models

 
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