Heater System GMC Vandura I

DESCRIPTION

System is a blend air type. Outside air is heated and then mixed with cooler outside air to attain desired temperature. System consists of blower and air inlet assembly, heater air distributor assembly, and heater control panel assembly.

Blower and air inlet assembly and water hoses are located on the engine side of dash panel while heater core and distributor duct are on passenger side. System has no water valve. Water circulation keeps heater core hot at all times.

Operation of blower motor is controlled by the fan switch. The motor is connected in series with the fan switch and blower resistor assembly.

On Van models, an auxiliary heater is available for heating rear of vehicle. The unit operates independently of standard heater and has its own set of controls. Heater hoses connect at the standard heater and extend from the standard heater to the auxiliary heater. A vacuum-operated water valve is installed in the inlet line in the engine compartment to cut off coolant flow when heat is not desired.

Temperature Control Lever

The lower lever on the control panel controls discharge air temperature in all Mode Control Lever positions. Full right position provides maximum heat. Full left position provides cool (outside) air.

Mode Control Lever (Standard System)

When in "OFF" position, the system is off. When in "HEATER" position, most of the air is delivered through the floor (heater) outlet with some air flow to the windshield (defroster) outlets.

The lever may be adjusted between "HEATER" and "DEF" to vary air distribution between floor air outlet and windshield outlet. In the "DEF" position, heated air is delivered to the windshield outlets with a small amount to the floor outlets.

Heater Control Panels. Scheme 1

Mode Control Lever (Optional System) S" Blazer & Pickup Models)

When this lever is in the "VENT" position, all discharge air is directed to the upper outlets. The "DEF" position directs most of the air to the windshield (defroster) outlets with some directed to the floor (heater) outlets. When in "HEATER" position, most of the air is delivered through the floor outlets with some air flow to the windshield outlets.

Blower Control

Blower control can be either knob or lever. Knob is a 4-speed type rotating from "OFF" to "HI". Lever is a variable speed type, sliding from "OFF" through "LO" to "HI".

Auxiliary Heater Water Valve

When heat is desired from auxiliary heater, and blower is in any position except "OFF", water valve can be opened to allow coolant flow to auxiliary heater. In "OFF" position, valve is closed to prevent coolant flow.

Auxiliary Heater Blower Switch

A 3-speed blower switch is located in the instrument panel to the right of steering column. When switch is in "OFF" position, auxiliary system will not operate.

Blazer & Pickup Models

Disconnect battery ground. Remove glove box and glove box door assembly. Pry off cable clip eyelet clip with pliers and disconnect cable from the door. Remove cable retaining screw. While holding cable with pliers, rotate the mounting tab on cable to adjust cable length. Reinstall cable by reversing removal procedure.

Van Models

Attach cable core wire and cable housing to control panel. Move temperature control lever to cool position and and attach loop on cable core wire to temperature door on heater case. Attach cable housing to heater/defroster assembly. Move temperature control lever to full heat position to adjust cable. (Scheme 3)

"S" Blazer & Pickup Models

Remove control panel. Disconnect control cables at both ends. Replace cables and install control panel. Cycle control lever through its full range of travel to adjust cable.

TROUBLE SHOOTING & DIAGNOSIS

See GENERAL MOTORS HEATERS - TROUBLE SHOOTING & DIAGNOSIS in this section.

Replacement (Blazer & Pickup Models)

Disconnect battery ground. Remove instrument panel bezel. Disconnect control cables and blower switch electrical connectors. Remove control panel through opening above it. Remove blower switch attaching screws and blower switch. Reverse removal procedure to install.

Replacement (Van Models)

1. Disconnect battery ground. Remove instrument panel bezel. Remove control panel to instrument panel retaining screws and carefully pull control panel rearward far enough to gain access to cables.
2. Disconnect control cables, light bulb and blower switch connector. Remove control panel from vehicle. Remove blower switch attaching screws and remove blower switch. To install, reverse removal procedure.

Replacement ("S" Blazer & Pickup Models)

Disconnect battery ground. Remove instrument panel center bezel. Remove control panel screws and pull control out. Disconnect electrical connection and cables from control panel. Remove blower switch from control panel. To install, reverse removal procedure.

1. Disconnect battery ground cable. Drain cooling system. Disconnect heater hoses at heater core, drain core into pan and plug openings. Remove nuts from heater distributor duct studs. Remove glove box and glove box door assembly. Disconnect control cables.
2. Remove floor outlet and remove defroster duct to heater distributor duct screw. Remove heater distributor to dash panel screws. Pull assembly rearward to gain access to wiring harness and disconnect all harness attached to assembly.
3. Remove assembly from vehicle. Remove heater core retaining straps and remove core. To install, reverse removal procedure. Make sure seals are intact before installing.

1. Disconnect battery ground. Drain cooling system. Remove coolant recovery tank. Disconnect heater hoses at core, drain coolant into pan and plug openings. Remove heater distributor duct to distributor case attaching screws and distributor duct to engine cover and remove duct.
2. Remove engine housing cover. Remove instrument panel attaching screws at windshield, all lower screws and right lower instrument panel support bracket at door pillar and engine housing. Lower steering column, then raise and support right side of instrument panel.
3. Remove defroster duct to distributor case attaching screw and 2 screws attaching distributor to heater case. Disconnect temperature door cable and fold back cable to provide access. (Scheme 3) Remove 3 nuts at engine compartment side of distributor case and 1 on passenger compartment side.
4. Remove heater case and core as an assembly. Tilt case assembly rearward at top while lifting up until core tubes clear dash openings. Remove core retaining straps and remove core. To install, reverse removal procedure. Make sure seals are intact before installing.

Disconnect battery ground cable. Drain engine coolant. Remove heater core hoses at core and plug core openings. Remove core cover attaching screws. Remove retainers at ends of core (4 screws). Remove core from vehicle. To install, reverse removal procedure.

Replacement (Blazer, Pickup & Van Models)

Disconnect battery ground. Disconnect blower motor lead wire. Remove 5 blower motor mounting screws and remove motor and wheel. If necessary, pry gently on the on the blower flange to remove. Remove the blower wheel to motor shaft nut and remove wheel from shaft. To install, reverse removal procedure.

Disconnect negative battery cable. Disconnect electrical connectors at blower motor. Remove blower motor retaining screws and remove blower motor. To install, reverse removal procedure.

Disconnect battery ground. Remove instrument panel bezel. Remove screws attaching control panel to instrument panel. Raise lower control and remove cable push nuts and tab attaching screws. Remove glove box and glove box door as an assembly. Remove cable from retaining clip and remove cable assembly. To install, reverse removal procedure. Check operation and adjust if necessary.

Control Cable Routing (Blazer and Pickup Models). Scheme 2

1. Disconnect battery ground. Remove glove box and glove box door assembly. Pry off cable clip eyelet clip from control assembly and heater/defroster assembly with pliers. Unsnap flags from receivers on heater/defroster assembly and control assembly.
2. Remove cable retaining screws on back of assembly heater/defroster assembly. Reinstall cable by reversing removal procedure. Test operation and adjust if necessary. (Scheme 3)

Control Cable Routing (Van Models). Scheme 3

Pull control panel out from dash. Disconnect cables at control panel and heater module. Remove cables. To install, reverse removal procedure.

Heater Wiring Diagram (Blazer and Pickup Models). Scheme 4

Heater Wiring Diagram ("S" Blazer and Pickup Models and Van Models). Scheme 5

Auxiliary Heater Wiring Diagram (Van Models). Scheme 6