How to replace Heater/evaporator Core on chev 1/2 ton pick up?

REMOVAL & INSTALLATION

CAUTION

Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, 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 quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

1991-98 C/K Series

1. Disconnect the negative battery cable.
2. Drain the cooling system.
3. Remove the instrument panel glove compartment.
4. Tag and unplug all electrical leads as necessary.
5. Remove the center air distribution duct from the floor.
6. If necessary, remove the ECM and mounting tray.
7. Remove the hinge pillar trim panels.
8. Remove the blower motor cover and then remove the motor.
9. Remove the steering wheel and tilt back the instrument panel slightly.
10. Remove the coolant overflow tank. Disengage the heater hoses at the core connections.
11. Unfasten the attaching screws and nut and then remove the heater case.
12. Remove the seven screws and lift off the heater case cover.
13. Remove the fasteners and brackets that hold the heater core to the case and lift the core from the case.

To install:

14. Install the heater core in the case.
15. Install the heater case bottom plate. Make sure there is a good seal.
16. Install the heater case into the truck. Tighten the 4 lower screws to 17 inch lbs. (2 Nm); the upper screw to 97 inch lbs. (11 Nm); and the nuts to 25 inch lbs. (2.8 Nm).
17. Connect the heater hoses at the core tubes.
18. Install the coolant overflow tank.
19. Install the instrument panel and the steering wheel.
20. Install the blower motor and cover.
21. Install the trim panels and if removed, the ECM. Install the air distribution duct and reconnect all electrical leads.
22. Install the glove compartment. Fill the cooling system and connect the battery cable.

1992-98 Models

1. Disconnect the negative battery cable and drain the engine coolant.
2. Remove the right rear quarter panel trim and then remove the panel itself.
3. Remove the right rear wheelhousing liner.
4. Disconnect the heater hoses from the core.
5. Unplug the electrical lead. Remove the drain valve.
6. Remove the heater module.
7. If necessary, remove the blower motor.
8. Remove the heater case cover.
9. Remove the heater case cover and then remove the heater core.

To install:

10. Install the heater core and then install the heater case cover.
11. If removed, install the blower motor.
12. Remove the heater module.
13. Attach the electrical lead. Install the drain valve.
14. Connect the heater hoses to the core.
15. Install the right rear wheelhousing liner.
16. Install the right rear quarter panel and then install the trim.
17. Connect the negative battery cable and fill the engine with coolant.

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Evaporator/ Heater Core Case

Remove or Disconnect

1. Negative battery cable.
2. Engine coolant.
3. Recover refrigerant.
4. Instrument panel.
5. Electrical connectors, as necessary.
6. Center floor air distribution duct.
7. ECM and mounting tray (diesel engines only).
8. Hinge pillar trim panels.
9. Blower motor cover.
10. Blower motor (60).
11. Steering column.
12. Tilt back instrument panel assembly.
13. Coolant recovery reservoir.
14. Heater hoses.
15. Evaporator tube.
16. Accumulator.
17. Screws (52 and 64).
18. Nut (50).
19. Screw (56).
20. Module assembly (57).

• May be necessary to have an assistant when removing module assembly.

1. Evaporator case bottom cover plate (63).

• Remove the seven screws that hold the cover plate to the module assembly.

1. Heater core and seal from module assembly.
2. Evaporator case cover (61).

• Remove the four screws that hold the case cover to the module assembly.

1. Evaporator core.

Install or Connect

1. Evaporator core.
2. Evaporator case cover (61).

• Install the four screws that hold the case cover to the module assembly.

1. Heater core and seal into module assembly.
2. Evaporator case bottom cover plate (63).

• Install the seven screws that hold the cover plate to the module assembly.

1. Module assembly (57).

• May be necessary to have an assistant when installing module assembly.

1. Screw (56).
2. Nut (50).
3. Screws (52 and 64).

Tighten

• Screw (56) to 11 Nm (97 lb in) .
• Nut (50) to 2.8 Nm (25 lb in) .
• Screws (52 and 64) to 1.9 Nm (17 lb in) .

1. Accumulator.
2. Evaporator tube.
3. Heater hoses.
4. Coolant recovery reservoir.
5. Instrument panel.
6. Steering column.
7. Blower motor (60).
8. Blower motor cover.
9. Hinge pillar trim panels.
10. ECM and mounting tray.
11. Center floor air distribution duct.
12. Electrical connectors, as necessary.
13. Engine coolant.
14. Negative battery cable.
15. Charge system.
16. Check system for leaks.

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Control Panel

See Figures 2 and 3

1. Disconnect the negative battery cable.
2. Remove the instrument panel bezel.
3. Remove the control panel-to-dash screws or release the snap-fit retainers using a small prytool.
4. Lower the control panel from the dash, without kinking the cable, and disconnect the cable, vacuum harness (if equipped) and electrical harness.

To install:

5. Connect the control cable, vacuum harness (if equipped) and electrical harness to the rear of the control assembly and position it into the dash.
6. If equipped, install the screws and tighten them to 17 inch lbs. (2 Nm).
7. If equipped with the snap-fit retainers, slide the assembly into the dash until the retainers engage.
8. Install the instrument panel bezel and connect the battery cable.

Fig. Fig. 2: Some front control assemblies are retained by screws...

Fig. Fig. 3: ... and some are retained by snap-fit retainers

Rear
Front Overhead

See Figure 4

1. Disconnect the negative battery cable.
2. Remove the roof console.
3. Pull the control panel out slightly, disconnect the electrical lead and then remove the control head.

To install:

4. Connect the lead and slide the panel back into the console.
5. Install the roof console and connect the battery cable.

Fig. Fig. 4: Rear control head assembly-front overhead console

Center Overhead

1. Disconnect the negative battery cable.
2. Remove the control panel bezel.
3. Pull the control panel out slightly, disconnect the electrical lead and then remove the control panel.

To install:

4. Connect the lead and slide the panel back into the console.
5. Install the bezel and connect the battery cable.

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