The heater unit, blower motor and heater core are all removed as a unit except where noted. Heater core and blower motor removal procedures are detailed within these Heater Unit/Heater Core procedures.
REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 and 221970-78 Pick-Ups
The heater core and blower motor are assembled into one unit which is centrally located in the passenger compartment. To effect repairs on either the core or blower motor, remove the entire assembly from the truck and separate the components with the unit removed.
- Drain the cooling system completely.
- Remove the package tray from under the dashboard.
- Unfasten the hose clamps holding the heater hoses to the core.
Hold a shallow pan under the hoses so that any water left in them will not run on the floor of the truck.
- Remove the defroster hoses from the heater case.
- Disconnect the heater control cables from the heater case.
- Remove the fresh air intake duct.
- Remove the electrical connector feeding the heater blower motor.
- There are four bolts holding the assembly to the inside of the cowl. Remove the bolts and withdraw the heater assembly from the passenger compartment.
- To remove the blower motor, tap the fan retaining nut slightly and then remove the nut from the shaft. Withdraw the fan. Remove the blower motor-to-heater case attaching screws and remove the motor.
- To remove the core, remove the heater control panel and heater lower case cover as a unit. The core may then be taken out of the heater case.
- Upon reassembly of the unit be sure to tighten all clamps to prevent leaks. Fill the cooling system with the correct mixture of coolant. With the heater off, run the engine to operating temperature. Open the heater control valve and see if the system is functioning properly.
Heater removal is basically the same with the following exceptions:
- Remove the glove box from the dashboard.
- Remove the heater controls from the dashboard.
- Remove the 3 bolt holding the unit in place.
- To remove the blower motor, remove the 3 screws on the blower motor housing and remove the motor.
- Turn off the water valve.
- Detach both hoses from the heater core.
- Unfasten the air duct clamp.
- Detach the defroster hoses from the heater box.
- Unfasten its attachment bolts and withdraw the core.
- Install the core into the case and tighten the bolts.
- Connect the defroster hoses to the heater case.
- Connect the air dust and the 2 heater hoses.
- Turn the water valve on, check the coolant level and check for any leaks.
The entire heater unit must be removed to gain access to the heater core. This procedure requires almost complete disassembly of the instrument panel and lowering of the steering column. If you decide to perform this operation, note the following points before proceeding.
- Be sure to tag any wiring which must be disconnected so that it may be correctly installed.
- As fasteners are removed, arrange them so that they may be installed in their original locations.
- Do not force any parts to remove them; if a part cannot easily be removed, remove any additional fasteners which may have been initially overlooked.
- When disconnecting coolant hoses, be careful not to damage the heater core tubes. Place a drain pan under the coolant hose connections before disconnecting the hoses.
- Disconnect the negative battery cable at the battery.
- Remove the glove box and the glove box door.
- Remove the lower heater ducts.
- Remove the large heater duct from the passenger side of the heater unit.
- Remove the ductwork from behind the instrument panel.
- Remove the radio, if so equipped.
- Disconnect the wiring connector from the right side inner portion of the glove opening.
- Remove the instrument panel pad (8 fasteners).
- Remove the hood release lever.
- Disconnect the hand throttle control cable.
- Remove the retaining screw from the left side of the fuse block.
- Remove the steering column-to-instrument panel attaching nuts and carefully lower the steering column. Tag and disconnect the wiring as necessary in order to lower the column assembly.
- Disconnect the electrical connector from the rheostat located to the left of the steering column opening.
- Remove the center duel outlet duct which is attached to the upper portion of the heater unit.
Remove the lower instrument panel. The fasteners are located in the following places:
- Left side of the instrument panel: two at the left side end and two at the left lower end.
- Above the steering column: two.
- To the right of the steering column opening: two.
- Left upper corner of the glove box opening: two.
- Left lower corner of the glove box opening: one.
- Right side of the instrument panel: two at the right side end and two at the right lower end.
- Tag and disconnect the hoses from the heater unit.
- Remove the heater unit-to-firewall fasteners and remove the heater unit.
- Remove the heater core pipe clamps from the heater unit. Also remove the heater core retaining clamp.
- Withdraw the heater core from the heater unit.
- Upon reassembly of the unit and installation in the vehicle, be sure to install all necessary parts in the reverse order of removal.
- Install heater hoses to heater unit. Install new clamps where necessary.
- Torque the steering column-to-instrument panel fasteners to 14-15 ft. lbs.
- Replenish the cooling system and check for leaks.
- Shut the water valve.
- Detach both of the hoses from the rear heater core.
- Detach the wiring from the rear heater.
- Unfasten the bolts and lift out the core.
- Install the heater core into the case and tighten the mounting bolts.
- Connect the electrical lead at the heater and then connect the 2 heater hoses to the core tubes.
- Open the water valve, fill the system with coolant and check for leaks.