A/c-Heater System - Manual — GMC Cab & Chassis R2500 (1987-1987)

MODEL IDENTIFICATION

CAUTION

When discharging air conditioning system, use only approved refrigerant recovery/recycling equipment. Make every attempt to avoid discharging refrigerant into the atmosphere.

Operation explanations, 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).

Model	Designation
Astro/Safari	M Series
Blazer/Jimmy & Pickup	R & V Series
S10 & S15	S & T Series
S10 Blazer & S15 Jimmy	S & T Series
Suburban	R & V Series
Van	G Series

GENERAL MOTORS MODEL DESIGNATION

DESCRIPTION

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

Auxiliary A/C systems are available. These systems operate in conjunction with the main system, and provide air conditioning only (auxiliary heater is a separate unit). Rear blower speed is independent of main system control. Rear blower may be operated even when front blower is off.

Mode Control Lever

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

Temperature Control Lever

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

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

Blower Switch

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

Auxiliary Blower Switch

Blower switch is the only control provided for auxiliary A/C system. In the "OFF" position, blower is inoperative, even though refrigerant is circulating through evaporator core if main system is operating. To operate auxiliary system, simply select desired blower speed. Auxiliary blower may be used for air circulation when main system is not in A/C mode.

"S/T" Series

Disengage temperature cable retaining clip from bellcrank post. Move temperature selector lever the full range of travel in both directions. Cable will automatically adjust. A "thud" should be heard at blend-air door open and closed positions.

All Other Models

Remove glove box and door. Loosen cable attaching screw at selector duct assembly. Make sure cable is installed in bracket on selector duct assembly. Place temperature selector lever in full COLD" position and hold while tightening cable attachment screw.

TROUBLE SHOOTING & DIAGNOSIS

See MANUAL A/C-HEATER SYSTEMS, GENERAL MOTORS PASSENGER CARS TRUCKS, TROUBLE SHOOTING & DIAGNOSIS in this section.

Removal (All Models)

Disconnect battery ground and compressor clutch connector. Discharge system using approved refrigerant recovery/recycling equipment. Disconnect accumulator inlet and outlet lines and cap or plug openings.
Remove accumulator bracket screws and remove accumulator from vehicle. Drain refrigerant oil from accumulator and measure quantity drained.

Installation

Measure an amount of clean refrigerant oil equal to that drained from accumulator and add an additional one oz. oil (2 oz. on S" series vehicles). Uncap new accumulator and add oil.
To complete installation, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Leak test, evacuate and recharge system.

Removal & Installation ("S/T" Series)

Disconnect battery ground. Remove vacuum tank. Remove blower motor flange attaching screws. Remove blower motor. To install, reverse removal procedure.

Removal & Installation (Astro/Safari)

Disconnect battery ground cable. Remove coolant bottle. Remove 2 bolts from washer bottle and secure out of way.
Remove heater from housing and remove squirrel cage from blower motor and remove both parts. To install, reverse removal procedure.

Removal & Installation (All Other Models)

Disconnect battery ground. Disconnect blower motor wires. Disconnect blower motor cooling tube. On Van models, remove coolant recovery tank and power antenna.
On all models, remove screws attaching blower motor to case and remove blower assembly. Remove nut attaching blower wheel to motor shaft and separate. To install, reverse removal procedure, using new sealant if necessary.

Scheme 3

Removal & Installation (All Models)

Disconnect battery ground. Disconnect rear duct assembly. Disconnect blower motor ground strap and lead wire. Support case assembly.
Remove lower-to-upper blower-evaporator case screws and lower the case and blower motor assembly. Remove retaining strap and remove motor and wheels. Remove wheels from motor shaft.
To install, position wheels on motor shaft making sure tension springs are installed on wheel hubs. Reverse removal procedure to complete installation, aligning wheels so they do not contact case. (Scheme 4)

Scheme 4

Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Disconnect battery ground. Remove upper fan shroud. Remove radiator. Remove shields from sides of radiator support. Remove condenser mounts.
Disconnect input and output lines from condenser and remove condenser from vehicle. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Leak test, evacuate and recharge system.

Removal & Installation ("G" Series)

Disconnect battery ground. Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove grille, hood lock, and center hood lock support as an assembly. Disconnect condenser inlet and outlet lines at condenser and cap openings. Remove screws attaching left side condenser bracket to radiator.
Remove screws attaching right side condenser bracket to condenser. Remove condenser from vehicle. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Add one oz. clean refrigerant oil to condenser. Leak test, evacuate and recharge system.

Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Disconnect battery ground. Remove grill and front panel. Remove radiator tie bar support at top. Disconnect lines for condenser and remove condenser. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Add one oz. clean refrigerant oil to condenser. Leak test, evacuate and recharge system.

Disconnect battery ground. Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove grille. Remove radiator grille center support. Remove left grille from upper fender support. Disconnect condenser inlet and outlet lines and cap openings. Remove condenser-to-radiator support screws.
Bend the left grille support outboard to gain clearance. Remove condenser from vehicle by pulling forward and lowering. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Add one oz. clean refrigerant oil to condenser. Leak test, evacuate and recharge system.

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

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

Disconnect battery ground. Remove headlight switch control knob. Remove instrument panel bezel. Remove control-to-instrument panel attaching screws. Remove temperature cable eyelet clip and mounting tab screw.
Pull control through instrument panel opening, pulling the lower right mounting tab through first, then the upper tab and finally the lower left tab. Disconnect electrical and vacuum connections and remove control panel from vehicle. To install, reverse removal procedure.

Disconnect battery ground. Remove radio. Remove instrument panel bezel. Remove control panel attaching screws and pull control panel out far enough to gain access to back of control panel.
Disconnect control cable, vacuum harness and electrical connectors at control panel. Remove control panel from vehicle. To install, reverse removal procedure.

Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Disconnect liquid line from the evaporator inlet. Cap opening on line. Using needle-nose pliers, remove expansion tube from evaporator core inlet line.

To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Insert the short screen end of the tube into the evaporator inlet line. (Scheme 5) Leak test, evacuate and recharge system.

Scheme 5

Scheme 5: Removal & Installation (All Models)

EXPANSION VALVE

Note. Expansion valve is used on auxiliary units that do not use external equalizer line.

Disconnect battery ground. Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove rear duct. Disconnect blower motor ground and lead wires. Support lower case and motor. Remove screws attaching case halves and lower case and motor assembly. Remove expansion valve sensing bulb clamps.
Disconnect valve inlet and outlet lines and remove expansion valve. Cap open connections. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Make sure bulb makes good contact with core outlet line. Leak test, evacuate and recharge system.

Scheme 6

Disconnect battery ground. Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove resistor screws and lay resistor aside with wires attached. Remove air cleaner attaching screws and lay air cleaner aside. Remove 5 screws and 2 nuts at case. Disconnect connector at A/C harness. Separate case halves and remove evaporator core cover.
Disconnect liquid line and evaporator-to-accumulator line. Remove screw attaching evaporator line bracket to accumulator bracket. Remove evaporator core including orifice tube from vehicle. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Leak test, evacuate and recharge system.

Disconnect battery ground. Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Disconnect resistor and lay wires out of way. Remove center air duct at air cleaner. Remove case attaching screws.
Remove accumulator suction hose. Remove evaporator connector at accumulator. Disconnect line from condenser, separate case halves and remove evaporator core. To install, Reverse removal procedure.

Disconnect battery ground. Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove coolant recovery tank and bracket. Disconnect all electrical connectors from core case assembly. Remove bracket at evaporator case. Remove right-hand marker lamp for access.
Disconnect accumulator inlet line and outlet line. Remove brackets attaching accumulator to case. Disconnect evaporator inlet line. Remove 3 nuts and screw attaching module to dash panel. Remove core case assembly from vehicle.
Remove screws and separate case sections. Remove evaporator core. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Add 3 oz. clean refrigerant oil to new condenser. Leak test, evacuate and recharge system.

Disconnect the battery ground. Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove nuts from selector duct studs projecting through the dash panel. Remove cover-to-dash and cover-to-case screws and remove evaporator case cover. Disconnect evaporator core inlet and outlet lines and cap openings.
Remove expansion tube. Remove evaporator core assembly. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Add 3 oz. clean refrigerant oil to evaporator. Leak test, evacuate and recharge system.

Disconnect battery ground. Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove rear duct. Disconnect blower motor ground and lead wires. Disconnect refrigerant lines at rear of evaporator-blower assembly. Cap openings. Remove screws attaching evaporator-blower assembly to roof rail.
Lower evaporator-blower assembly and place on a work bench upside down. Remove case half attaching screws and remove upper case half from evaporator core. Remove expansion valve inlet and outlet lines and cap openings. Remove expansion valve capillary bulb from evaporator outlet line and remove valve.
Remove plastic pins holding screen to core and remove screen. To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Make sure capillary bulb has good contact with line. Add 3 oz. clean refrigerant oil to new core. Leak test, evacuate and recharge system.

Scheme 7

Disconnect battery ground. Disconnect drain tube from rear duct. Remove screws attaching duct to roof panel and rear header brackets. Remove duct. To install, reverse removal procedure.

HEATER CORE

Note. These procedures are for vehicles with manual A/C-heater systems only. For replacement on vehicles equipped with heater systems, see appropriate article in HEATER SYSTEMS, GENERAL MOTORS TRUCKS section.

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

Disconnect battery ground. Drain coolant. Disconnect heater hoses at heater core and plug openings. Remove core cover attaching screws. Remove retainers at core ends and remove core. To install, reverse removal procedure.

Disconnect battery ground. Remove engine cover. Remove steering column-to-instrument panel attaching bolts and lower column. Remove upper and lower instrument panel attaching screws and radio support bracket attaching screw. Raise and support right side of instrument panel.
Remove right lower instrument panel support bracket. Remove recirculating air door vacuum actuator. Disconnect temperature cable and vacuum hoses at distributor case. Remove heater distributor duct. Remove 2 defroster duct-to-dash panel attaching screws. From engine compartment, disconnect heater hoses and plug.
Remove 3 nuts attaching heater core case to dash panel and screw at lower right corner. Remove heater distributor from vehicle. Remove gasket to expose screws attaching case sections together. Remove temperature cable support bracket. Remove case attaching screws and separate case. Remove heater core. To install, reverse removal procedure.

Disconnect battery ground. Drain radiator and disconnect heater hoses from heater core. Plug openings. Remove glove box and door. Remove screws attaching center duct to selector duct and instrument panel. Remove center ducts (lower and upper). Disconnect temperature control cable at blend-air door.
Remove nuts from the 3 selector duct studs projecting through dash. Remove screw attaching selector duct to dash. Pull selector duct rearward until heater core tubes clear the dash panel. Lower selector duct far enough to gain access to vacuum and electrical harnesses.
Disconnect vacuum and electrical harnesses. Remove selector duct assembly. Remove core mounting straps and core. To install, reverse removal procedure and adjust temperature control cable.