A/c-Heater System - Manual GMC Typhoon I

A/C SYSTEM SPECIFICATIONS

SPECIFICATIONS

DESCRIPTION

SYSTEM DESCRIPTION

A/C-heater system is a blend-air system. Air entering vehicle must pass through evaporator core and through, or around, heater core to provide air of desired temperature. Compressor operation is controlled by a pressure cycling switch on top of accumulator.

Temperature Control Lever

Temperature control lever regulates temperature of air entering passenger compartment through a cable-operated blend-air door. In COLD position, air by-passes heater core to provide maximum cooling.

In other positions, air chilled by evaporator core and heated air from heater core are mixed to provide air of desired temperature. In HOT position, A/C system should be off to provide maximum heating.

Mode Selector Lever

Mode selector lever controls a vacuum-operated selector valve to operate air door motors, providing desired air distribution. Lever also allows for selection of air conditioning or heating functions, including defroster air distribution.

Blower Switch

Blower switch is a 4-position lever with LOW, HI and 2 intermediate positions. Blower operates in any mode control lever position except OFF.

CONTROL CABLE

Remove cable retainer at heater and remove cable. Bend control cable to lengthen or shorten cable. Install cable and retainer. Cycle control lever through its full range of travel. If necessary, readjust cable.

TROUBLE SHOOTING

Note. Also see MANUAL A/C-HEATER TROUBLE SHOOTING article in this section.

A/C COMPRESSOR DOES NOT OPERATE

Note. Outside temperature must be above 60°F (16°C) to properly diagnose system.

Note. Information on vehicles with 2.8L engine is not available .

2.5L Models

1. Turn ignition switch to RUN position. Place mode selector lever in NORM position. Connect test light from Dark Green wire at A/C compressor clutch connector to ground. If test light glows, go to step 3). If test light does not glow, go to next step.
2. Connect test light from Dark Green wire at A/C compressor control relay connector (located in engine compartment on left side cowl) to ground. If test light does not glow, go to step 4). If test light glows, repair open circuit in Dark Green wire between A/C compressor clutch connector and A/C compressor control relay connector.
3. Connect test light from Dark Green wire to Black wire at A/C compressor clutch connector. If test light glows, replace A/C compressor clutch. If test light does not glow, repair open circuit in Black wire between A/C compressor clutch connector and ground.
4. Connect test light from Dark Green/White wire at A/C compressor control relay connector to ground. If test light does not glow, go to next step. If test light glows, connect test light from Pink/Black wire at A/C compressor control relay connector to ground. If test light glows, go to step 6). If test light does not glow, repair open circuit in Pink/Black wire between A/C compressor control relay connector and fuse block.
5. Connect test light from Dark Green wire at low pressure switch (located on A/C compressor) to ground. If test light does not glow, go to step 8). If test light glows, repair open circuit in Dark Green wire between low pressure switch connector and A/C compressor control relay connector. See «WIRING DIAGRAMS»(/gmc/typhoon/i-1991-1993/remont/manual-hvac-system/#ac-heater-system-manual) .
6. Disconnect A/C compressor control relay. Connect jumper wire from Pink/Black wire terminal of relay to positive battery terminal. Connect another jumper wire from Red wire terminal of relay to negative battery terminal. Connect an ohmmeter from Dark Green/White wire terminal to Dark Green wire terminal of relay. If continuity does NOT exist across relay terminals, replace A/C compressor control relay.
7. If continuity exists across relay terminals, connect A/C compressor control relay. Repair open circuit in Red wire between A/C compressor control relay connector and Electronic Control Module (ECM) connector. If wire is okay, check ECM A/C compressor clutch control circuit. See appropriate article in the ENGINE PERFORMANCE Section.
8. Connect test light from Light Green wire at low pressure switch connector to ground. If test light glows, replace low pressure switch. If test light does not glow, go to next step.
9. Connect test light from Light Green wire at mode selector control to ground. If test light does not glow, go to next step. If test light glows, repair open circuit in Light Green wire between mode selector control connector and low pressure switch connector.
10. Connect test light from Brown wire at mode selector control to ground. If test light glows, replace mode selector control. If test light does not glow, repair open circuit in Brown wire between mode selector control connector and fuse block.

Note. Information on vehicles with 2.8L engine is not available .

4.3L Models

1. Turn ignition switch to RUN position. Place mode selector lever in NORM position. Connect test light from Dark Green wire at A/C compressor clutch connector to ground. If test light glows, go to next step. If test light does not glow, repair open circuit in Dark Green wire between A/C compressor clutch connector and evaporator pressure switch connector (located on accumulator). If wire is okay, go to step 3).
2. Connect test light from Dark Green wire to Black wire at A/C compressor clutch connector. If test light glows, replace A/C compressor clutch. If test light does not glow, repair open circuit in Black wire between A/C compressor clutch connector and ground. See «WIRING DIAGRAMS»(/gmc/typhoon/i-1991-1993/remont/manual-hvac-system/#ac-heater-system-manual) .
3. Connect test light from Light Green wire at evaporator pressure switch connector to ground. If test light glows, replace evaporator pressure switch. If test light does not glow, connect test light from Light Green wire at mode selector control to ground. If test light DOES NOT light, go to step 5).
4. If test light glows, repair open circuit in Light Green wire between evaporator pressure switch connector and connector located behind radio (at center of instrument panel), or between connector behind radio and mode selector control connector.
5. Connect test light from Brown wire at mode selector control connector to ground. If test light glows, replace mode selector control. If test light does not glow, repair open circuit in Brown wire between mode selector control connector and connector located behind instrument panel (to right of steering column), or between connector located behind instrument panel and fuse block.

BLOWER MOTOR INOPERATIVE

1. Disconnect blower motor connector. Turn ignition switch to RUN position. Place mode selector lever in NORM position. Place blower switch to HI position. Connect test light from Purple wire at blower motor connector to ground. If test light glows, go to next step. If test light does not glow, go to step 3).
2. Connect test light from Purple wire to Black wire at blower motor connector. If test light glows, replace blower motor. If test light does not glow, repair open in Black wire between blower motor connector and ground.
3. Connect test light from Brown wire (mode selector control to fuse block wire) at mode selector control to ground. If test light glows, go to next step. If test light does not glow, repair open circuit in Brown wire between mode selector control and fuse block.
4. Connect test light from Brown wire (mode selector control to blower switch wire) at mode selector control to ground. If test light does not glow, replace mode selector control. If test light glows, go to next step.
5. Connect test light from Brown wire at blower switch connector to ground. If test light glows, go to next step. If test light does not glow, repair open circuit in Brown wire between mode selector control connector and blower switch connector. See «WIRING DIAGRAMS»(/gmc/typhoon/i-1991-1993/remont/manual-hvac-system/#ac-heater-system-manual) .
6. Connect test light from Orange wire at blower switch connector to ground. If test light does not glow, replace blower switch. If test light glows, go to next step.
7. Connect test light from Orange wire at high blower relay connector (located near blower motor) to ground. If test light glows, go to next step. If test light does not glow, repair open circuit in Orange wire between high blower relay connector and blower switch connector.
8. Connect test light from Orange wire to Black wire at high blower relay. If test light does not glow, replace high blower relay. If test light glows, connect test light from Purple wire at high blower relay connector to ground. If test light does not glow, replace high blower relay. If test light glows, repair open circuit in Purple wire between high blower relay connector and blower motor connector.

BLOWER MOTOR OPERATES IN LO AND/OR MED ONLY

1. Connect test light from Orange wire at high blower relay connector (located near blower motor) to ground. If test light does not glow, go to step 3). If test light glows, connect test light from Orange wire to Black wire at high blower relay connector. If test light glows, go to next step. If test light does not glow, repair open circuit in Black wire between high blower relay connector and ground.
2. Connect test light from Red wire at high blower relay connector to ground. If test light glows, replace high blower relay. If test light does not glow, repair open circuit in Red wire between high blower relay connector and battery junction block (located in engine compartment on center of cowl). See WIRING DIAGRAMS.
3. Turn ignition switch to RUN position. Place mode selector lever in NORM position. Place blower switch in HI position. Connect a test light from Orange wire at blower switch connector to ground. If test light does not glow, replace blower switch. If test light glows, repair open circuit in Orange wire between blower switch connector and blower relay connector.

BLOWER MOTOR DOES NOT OPERATE IN LO

1. Turn ignition switch to RUN position. Place mode selector lever in NORM position. Place blower switch in LO position. Connect test light from Dark Blue wire at high blower relay connector (located near blower motor) to ground. If test light does not glow, go to next step. If test light glows, replace high blower relay.
2. Connect test light from Dark Blue wire at blower resistor connector (located in blower assembly) to ground. If test light glows, repair open circuit in Dark Blue wire between blower resistor connector and high blower relay connector. If test light does not glow, connect test light from Tan wire at blower resistor connector to ground. If test light does not glow, go to next step. If test light glows, replace blower resistor.
3. Connect test light from Tan wire at blower switch connector to ground. If test light does not glow, replace blower switch. If test light glows, repair open circuit in Tan wire between blower switch connector and blower resistor connector. See WIRING DIAGRAMS.

Removal & Installation

1. Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Disconnect electrical connections (if necessary). Disconnect accumulator inlet and outlet lines, and plug openings. Remove accumulator bracket screws and accumulator. (Scheme 15)
2. Add 3.5 ounces of clean refrigerant oil to NEW accumulator prior to installation. To complete installation, reverse removal procedure. Install NEW "O" rings lubricated with clean refrigerant oil prior to installation. Evacuate, recharge and leak test system.

Scheme 15

Disconnect negative battery cable. Disconnect blower motor electrical connections. Remove blower motor attaching screws. Remove blower motor. Remove nut attaching blower fan to blower motor shaft, and remove fan. To install, reverse removal procedure. (Scheme 15)

1. Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove upper fan shroud. Drain engine coolant. Remove radiator.
2. Disconnect inlet and outlet lines at condenser, and cap openings. Remove condenser from vehicle. To install, reverse removal procedure. Install NEW "O" rings lubricated with clean refrigerant oil prior to installation. Add one ounce of clean refrigerant oil to condenser. Fill cooling system and check for leaks. Evacuate, recharge and leak test A/C system.

Disconnect negative battery cable. Remove instrument panel center bezel. Remove control panel attaching screws. Remove control cable, and disconnect vacuum and electrical connectors at control panel. Remove control panel. To install, reverse removal procedure.

1. Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Drain engine coolant. Remove heater hoses from core. Remove resistor and electrical connectors (if necessary). Disconnect line from condenser to evaporator. Remove hose assembly from accumulator. Remove accumulator.
2. Remove blower motor assembly. Remove case screws and nuts. Separate case halves and remove evaporator core. (Scheme 15) To install, reverse removal procedure. Install NEW "O" rings lubricated with clean refrigerant oil prior to installation. Fill cooling system and check for leaks. Evacuate, recharge and leak test A/C system.

HEATER CORE

Disconnect negative battery cable. Drain engine coolant. Remove heater hoses at core, and plug core openings. Remove core cover attaching screws. Remove retainers at end of core. Remove heater core. To install, reverse removal procedure. Fill cooling system and check for leaks.

Scheme 16

1. Discharge A/C system using approved refrigerant recovery/recycling equipment. Disconnect inlet line from evaporator inlet, and cap inlet opening. Using needle-nose pliers, remove orifice tube from evaporator core inlet line.
2. To install, reverse removal procedure. Install NEW "O" rings lubricated with clean refrigerant oil prior to installation. Insert short screen end of orifice tube first. Evacuate, recharge and leak test system.

Scheme 17

A/C Sys Wiring Diagram ("S" Series - 2.5L Engine). Scheme 18

A/C Sys Wiring Diagram ("S" Series - 2.8L). Scheme 19

See also:
• WIRING DIAGRAMS