Heater System GMC Suburban R1500

MODEL IDENTIFICATION

Operation, adjustments, removal and installation procedures in this article are referred to by model name or designation (body type). The following table lists General Motors model name and designation (body type).

GENERAL MOTORS MODEL DESIGNATION

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 a blower and an air inlet assembly, heater air distributor assembly and heater control panel.

Blower, air inlet assembly and heater hoses are located on the engine side of dash panel while heater core and distributor duct are on passenger side. System has no heater control valve. Coolant 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 all Van and Suburban 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 heater control valve is installed in the inlet line in the engine compartment to cut off coolant flow when heat is not desired. (Scheme 7)and (Scheme 8).

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.

MODE CONTROL LEVER (OPTIONAL SYSTEM ASTRO/SAFARI, "C", "K", "S" & "T" SERIES)

When lever is in "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 into the flow (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 type. 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 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/Jimmy, "R" & "V" Series

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

Astro/Safari & "G" Series

Attach cable core wire and cable housing to control panel. Move temperature control lover to cool position 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.

"S" & "T" Series

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.

Removal & Installation (Astro/Safari, Blazer/Jimmy, "C", "K", "R" & "V" Series)

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. To install, reverse removal procedures.

Removal & Installation ("G" Series)

1. Disconnect battery ground. Remove instrument panel bezel. Remove control panel-to-instrument panel retaining screws. 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 procedures.

Removal & Installation ("S" & "T" Series)

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 procedures.

HEATER CORE

Note. These procedures are for vehicles with heater systems. For vehicles with manual A/C-heater systems, see appropriate MANUAL A/C-HEAT SYSTEMS article.

Removal & Installation (Astro/Safari)

Disconnect battery ground. Drain coolant. Remove coolant bottle. Remove bolts from washer bottle and move out of way. Remove heater hoses at core and plug openings. Remove core cover attaching screws. Remove heater core retaining straps and remove core. To install, reverse removal procedures. (Scheme 1)

Scheme 1

Removal & Installation (Blazer/Jimmy, "R" & "V" Series)

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. Remove defroster duct-to-heater distributor duct screw. Remove heater distributor-to-dash panel screws. Pull assembly rearward to gain access to wiring harness. Disconnect all harness connectors attached to assembly.
3. Remove assembly from vehicle. Remove heater core retaining straps and remove cores. To install, reverse removal procedures. Ensure seals are intact before installing.

Removal & Installation ("C" & "K" Series)

1. Disconnect negative battery cable. Drain cooling system. Remove coolant recovery tank. Disconnect heater hoses at core. Disconnect cable from antenna mast. Remove glove box.
2. Disconnect wiring harness from ECM. Remove ECM and bracket. Remove right kick pad. Remove right lower dash panel bolt and nut.
3. Remove heater case mounting bolts. Remove heater case from vehicle, raising instrument panel for additional room. Remove heater core from heater case. To install, reverse removal procedure. (Scheme 2)

Scheme 2

1. Disconnect battery ground. Drain cooling system. Remove coolant recovery tank. Disconnect heater hoses at core. Drain coolant into pan and plug openings. Remove screws attaching heater duct at case and distributor duct to engine cover. Remove ducts.
2. Remove engine housing cover. Remove instrument panel attaching screws at windshield. Remove all lower screws and right lower instrument panel support bracket at door pillar. Remove engine housing. Lower steering column, then raise and support right side of instrument panel.
3. Remove defroster duct-to-distributor case attaching screw and screws attaching distributor to heater case. Disconnect temperature door cable and bolt back cable to provide access. Remove nuts at engine compartment side of distributor case and nut 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 cores. To install, reverse removal procedures. Ensure seals are intact before installing.

Removal & Installation ("S/T" Series)

Disconnect battery ground cable. Drain engine coolant. Remove heater core hoses at core and plug core openings. Remove cores cover attaching screws. Remove retainers at end of core. Remove cores from vehicle. To install, reverse removal procedures. (Scheme 3)and (Scheme 4).

Scheme 3

Scheme 4

Disconnect negative battery cable. Disconnect blower electrical connections and remove coolant bottle. Remove bolts from washer bottle and move out of way. Remove blower motor retaining screws and remove blower. To install, reverse removal procedures.

Removal & Installation (Blazer/Jimmy, "C", "G", "K", "R" & "V" Series)

Disconnect negative battery cable. On Vans, remove coolant recovery tank and power antenna. On all models, disconnect blower motor lead wire. Remove blower motor mounting screws. Remove motor and wheel. If necessary, pry gently on the blower flange to remove. Remove the blower wheel-to-motor shaft nut and remove wheel from shaft. To install, reverse removal procedures.

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

Removal & Installation (Astro/Safari, "S" & "T" Series)

Disconnect negative battery cable. Pull control panel out from dash. Disconnect cables at control panel and heater module. Remove cables. To install, reverse removal procedures. (Scheme 5)and (Scheme 6).

Scheme 5

Scheme 6

Removal & Installation (Blazer/Jimmy, "C", "K", "R" & "V" Series)

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 procedures. Check operation, and adjust if necessary. see scheme 7

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

Scheme 7

Scheme 8