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. |
Adjustment and repair procedures in this article are referred to by either model or body type. The following table lists General Motors division, model name, and body type. Only models referred to in this article by body type are listed in the table.
| Body Type & GM Division | Model Name | |
|---|---|---|
| A Body | ||
| Buick | Century | |
| Chevrolet | Celebrity | |
| Oldsmobile | Cutlass Ciera | |
| Pontiac | 6000 | |
| B Body | ||
| Buick | LeSabre | |
| Chevrolet | Impala, Caprice | |
| Oldsmobile | 88 | |
| Pontiac | Parisienne | |
| G Body | ||
| Buick | Regal | |
| Chevrolet | Malibu, El Camino, Monte Carlo | |
| Oldsmobile | Cutlass | |
| Pontiac | Bonneville, Grand Prix | |
| J Body | ||
| Buick | Skyhawk | |
| Cadillac | Cimarron | |
| Chevrolet | Cavalier | |
| Oldsmobile | Firenza | |
| Pontiac | 2000 | |
| X Body | ||
| Buick | Skylark | |
| Chevrolet | Citation | |
| Oldsmobile | Omega | |
| Pontiac | Phoenix | |
GENERAL MOTORS MODELS
DESCRIPTION
All models use the cycling clutch orifice tube (CCOT) to meter the flow of refrigerant into the evaporator. A pressure cycling (sensing) switch cycles the compressor on and off to maintain the desired cooling and to prevent evaporator freeze-up.
Either the 4-cylinder radial or one of the two 6-cylinder axial compressors (A-6 or DA-6) is used, depending on engine and body style.
UNCONDITIONED AIR
Air, either outside or recirculated, enters the system and is drawn through the evaporator core. There it receives maximum cooling if the control levers are set for the cooling mode of operation.
After leaving the evaporator, the air is forced by the blower into the heater and A/C selector duct assembly.
By means of a cable-controlled temperature door, the air is caused to pass either through or around the heater core in the proper proportions to obtain the desired discharge air temperature.
CONDITIONED AIR
Discharge air may be directed to either the floor and defroster outlets or to the dash outlets by a vacuum-actuated diverter door. If the air is not directed to the dash outlets, another vacuum-operated door directs air flow to either the floor outlets or the defroster outlets.
During cooling modes of operation, if the air is cooled below the comfort level, it is then warmed by the heater core to arrive at the desired temperature by adjusting the temperature control lever.
MODE SELECTOR LEVER
Several settings are possible on the control panel to provide just the comfort level desired. Upper lever is mode selector lever. (Scheme 1) Typical mode settings are as follows
"OFF"
No blower operation occurs in this position. No conditioning takes place.
General Motors Manual A/C Control Panel Blower fan control design varies between models. Scheme 1
"MAX"
Maximum cooling is provided in this setting. Conditioned air is distributed through dash outlets, with a slight amount to the floor at any blower speed.
"NORM"
Conditioned air is directed through dash outlets, and a slight amount to floor.
"BI-LEVEL"
Conditioned air is directed through dash and floor outlets, with some also to windshield.
"VENT"
In this position the compressor is not operating. Outside air is delivered through dash outlets.
Compressor does not operate in this position. Outside air is heated and distributed, about 80% to floor and 20% to windshield and side windows.
"DEFROST"
In this position, conditioned air is distributed, about 80% to windshield and side windows and 20% to floor.
Typical Heater-A/C Module Note relationship of various components. Scheme 2
TEMPERATURE LEVER
When the "VENT" or "HEATER" modes are selected by use of the mode selector lever, the A/C compressor and evaporator are not in operation. Ambient air is warmed to the level desired by adjustment of the temperature control lever.
If the temperature lever is placed at "COLD", no airflow is allowed through the heater core. If the lever is placed at "HOT", all air flows through the heater core.
PRESSURE CYCLING SWITCH
Located near the top of the accumulator, the switch cycles the compressor on at 41-51 psi and off at 20-28 psi. Switch also turns off compressor in event of low refrigerant charge or cold (below 37°F) ambient temperatures.
PRESSURE RELIEF VALVE
Mounted on rear of compressor, the valve opens automatically when discharge side pressure reaches approximately 440 psi, preventing damage from excessive pressure.
ACCUMULATOR
The accumulator is a refrigerant-storing device, located at the evaporator outlet. This unit receives vapor, accompanying liquid, and refrigerant oil from the evaporator.
An oil bleed hole is located in the lower portion of the accumulator, assuring return of the oil to the compressor. This prevents oil from being trapped in the accumulator. A bag of desiccant is located in the bottom of the accumulator. (Scheme 3)
Schematic Showing Accumulator Operation Accumulator keeps liquid R-12 from reaching compressor. Scheme 3
EXPANSION TUBE
The expansion tube is located in the evaporator inlet. It controls the flow of liquid refrigerant into the evaporator. The expansion tube replaces the previously used expansion valve.
The tube has no moving parts and is not adjustable. If defective, it must be replaced as a unit. (Scheme 4)
CCOT System Expansion Tube Be sure to install tube properly. Scheme 4
WIDE-OPEN THROTTLE CUT-OUT SWITCH
This switch, located on the carburetor or accelerator pedal bracket, is used on some models to stop compressor operation under full load, improving acceleration..
Camaro & Firebird (4-Cyl. Only) "A", "J", & "X" Bodies
The power steering cut-off switch is used to stop compressor operation when power steering pressure exceeds a preset level. This reduction in engine load prevents stalling during parking.
"A", "J", & "X" Bodies
The high pressure switch stops compressor operation if high side pressure exceeds 410-450 psi. The switch prevents compressor damage and loss of refrigerant. After pressure drops below 150-250 psi, compressor operation resumes.
LOW PRESSURE CUT-OFF SWITCH
Compressor protection is offered on some models by a low pressure cut-off switch that opens in event of a low refrigerant charge.
Chevette & T1000
This relay prevents the compressor from operating for 10 seconds after the engine is started or A/C mode is selected.
When system is operating, current is applied to idle stop solenoid of automatic transmission models to increase engine idle speed. It also stops the compressor if engine temperature light comes on due to overheating.
COMPRESSOR CONTROL RELAY
Compressor operation is cut off on some models under certain operating conditions by the A/C control relays, wide-open throttle, low air temperature, and low engine speed.
CONSTANT RUN RELAY
On some models, engine idle quality is maintained by this relay. It eliminates compressor cycling during engine idle for a predetermined time after vehicle has come to rest from road speed. Relay is controlled by ECM and engine sensors.
"J" Bodies
The delay timer is located behind the left-hand shock tower. When the pressure cycling switch closes, a signal is sent to the electronic control module and delay timer.
Contacts in the delay timer open, while the ECM adjusts engine controls for A/C load. After 3 to 4 seconds, the delay timer contacts close, and current flows to A/C clutch.
The delay timer inhibitor is also located behind left-hand shock tower. When engine speed is above 1400 RPM, no delay is required, so the delay timer inhibitor removes power from the delay timer.
TEMPERATURE CUT-OFF RELAY
Some models are equipped with a temperature cut-out relay, operated by a temperature switch in the coolant system. If engine temperature rises to an excessive level, the switch opens, the relay opens, and compressor operation is interrupted.
AIR TEMPERATURE SENSOR
Some vehicles use an air temperature sensor to prevent compressor operation, when ambient air temperature falls below a preset level.
"B", "C", & "G" Bodies
- Although cable is self-adjusting, an initial setting should be made to obtain correct adjustment. Disengage temperature cable retaining clip from bellcrank post. Position threaded operating rod so that it extends 3/8" beyond outer edge of white nylon retaining button.
- Reassemble temperature cable retaining clip to bellcrank vertical post. Operate lever its full travel in both directions (full "HOT" to full "COLD") to automatically adjust cable. Temperature door thud should be heard at both ends of lever movement.
Riviera & Toronado
- Position temperature lever 1/16" from full "COLD" position, and turn cable adjuster until temperature door is seated. Move temperature lever to Full "HOT" and back to "COLD".
- Lever should stop slightly short of each end of slot, and a thump should be heard as door seats in each position. If door is not heard seating, or if lever is more than 1/8" from end of slot, repeat adjustment.
Attach cable to control assembly, and place temperature lever in "COLD" position. Place cable loop on heater case temperature door post. Push cable housing toward adjustment lever until door seats and there is no slack in cable. Tighten cable clamp screw.
- Move control lever to maximum "COLD" position. Adjust turnbuckle until control lever moves 1/8" back from end of slot.
- Move control lever to maximum "HEAT" position, and then back to maximum "COLD" position. If lever does not spring back or exceeds 1/8" spring back, repeat adjustment.
TROUBLE SHOOTING & DIAGNOSIS
See 1983 GENERAL MOTORS MANUAL A/C TROUBLE SHOOTING AND DIAGNOSIS article.
Replacement (All Models)
- Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Disconnect condenser-to- evaporator line at evaporator inlet. Using special tube removal tool or needle nose pliers, remove expansion tube and "O" ring from inlet line.
- If removal of orifice tube is difficult, remove as much of impacted residue as possible. Using a heat gun, hair drier, or equivalent, apply heat 1/4" from dimples on inlet pipe. Do not overheat pipe. NOTE: If vehicle is equipped with a pressure switch (mounted near orifice tube location), remove switch to avoid damage to switch when heating inlet tube.
- To install, reverse removal procedure. Using new "O" ring, coated with refrigerant oil, install orifice tube with short screen end first. Evacuate and charge system.
- The fitting on the accumulator is equipped with a Schrader-type valve, making system discharge unnecessary. Disconnect battery ground cable and wires at switch.
- Unscrew switch from accumulator. Lubricate new "O" ring with refrigerant oil, and install switch. Do not overtighten.
- Disconnect battery ground cable, and discharge system using approved refrigerant recovery/recycling equipment. Disconnect inlet and outlet lines. Cap all open fittings and lines. Remove electrical connections and pressure cycling switch.
- Remove accumulator mounting screws and accumulator.
- Measure amount of refrigerant oil in accumulator. Fill new accumulator with same amount plus 2 oz. of new refrigerant oil.
- To install, reverse removal procedure. Use new "O" rings, lubricated with refrigerant oil, when installing fittings. Evacuate and recharge system.
Replacement ("J" Bodies)
- Discharge system using approved refrigerant recovery/recycling equipment. Hoist car and remove front, left-hand, and right-hand air dams and lower fascia-to-fender bolts. Disconnect lower line at condenser. Lower car, and remove both core support-to-fascia filler panels, mounting brackets, and hood latch.
- Remove head lamp bezels, upper fascia-to-fender bolts and pull fascia forward. Disconnect upper condenser line. Remove condenser brackets and condenser.
Scheme 5
- Disconnect battery and discharge system using approved refrigerant recovery/recycling equipment. Remove radiator brackets, grille support, or fan shroud as necessary. Disconnect inlet and outlet line and cap fittings. If necessary, tilt radiator rearward, and remove condenser. (Scheme 5) (Scheme 5): Typical Condenser Location and Installation
- To install, reverse removal procedure and add 2 oz. of refrigerant oil to condenser. Evacuate and charge system.
Replacement ("B", "C", & "G" Bodies)
- Blower resistor is mounted on blower side of blower-evaporator case of "B" body models or on evaporator cover of "G" body vehicles.
- Disconnect battery ground cable and resistor wiring harness connector. Remove 2 resistor mounting screws, and remove resistor. To install, reverse removal procedure.
EVAPORATOR CORE
Note. Heater core removal and evaporator core removal are covered in one procedure for some models. See EVAPORATOR AND HEATER CORE.
Replacement (Camaro & Firebird)
- Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove accumulator. Remove 2 attaching screws, and remove high blower relay terminal. Remove upper case screws, relocate wiring harness, and remove dipstick.
- Disconnect liquid line fitting. Remove upper case, and lift evaporator core out of case. Reverse removal procedure to reinstall.
Replacement (Chevette & T1000)
- Disconnect battery, and discharge system using approved refrigerant recovery/recycling equipment. Remove heater core case-to-distributor assembly screws (not heater hoses). Roll assembly forward, away from distributor case. Remove accumulator and brackets.
- Remove temperature door cable and door arm access cover. Position control door arm out of way. Remove blower motor.
- Remove sealer from exposed portion of outlet tube at surface of evaporator case. Remove screws and case. Remove evaporator core. To install, reverse removal procedure. Add 3 oz. of refrigerant oil, and evacuate and recharge system.
Replacement (Riviera & Toronado)
- Disconnect battery ground cable, and discharge system using approved refrigerant recovery/recycling equipment. Remove blower relay, resistor, and ground wires. Remove vacuum tank. Disconnect condenser line from evaporator and suction line from accumulator.
- Disconnect blower wires, and remove blower assembly. Raise car, and remove 2 screws and 1 nut from evaporator assembly. Remove 2 screws and 1 nut from top of assembly. Remove evaporator assembly, including insulator on diesel models.
- Disconnect accumulator line, and remove accumulator. Remove evaporator from case. To install, add 3 oz. refrigerant oil to evaporator, and reverse removal procedure. Apply new sealant around case, and evacuate and charge system.
Replacement ("A" & "X" Bodies With Gasoline Engines)
- Disconnect battery ground cable and discharge system using approved refrigerant recovery/recycling equipment. Remove air cleaner, disconnect electrical connection to A/C system along cowl, and move harness to right-hand side car. Remove vacuum tank.
- Disconnect refrigerant lines at evaporator and accumulator inlets. Remove outer blower case to-cowl screws, and remove blower case assembly from vehicle. Remove evaporator core from housing.
- Add 3 oz. new refrigerant oil to evaporator. Place core in housing. Install housing on cowl, using new sealant. Reverse removal procedure to complete installation. Evacuate and charge system.
Replacement ("A" Bodies With Diesel Engine)
- Remove air cleaner and install J-26996-1 cover. Disconnect negative battery cables, and discharge system using approved refrigerant recovery/recycling equipment. Disconnect A/C electrical connections along cowl, and move harness to right-hand side of vehicle.
- Remove vacuum tank. Disconnect evaporator and accumulator inlet lines. Remove engine support strut. Position floor jack under front crossmember of cradle. Raise jack until it just starts to raise vehicle.
- Remove 2 front body mount bolts (No. 1 and 3), with lower cushions and retainer. Remove cushions from bolts. Reinstall body mount bolts, with retainers installed. Turn at least 3 turns into cage nuts, so bolts limit cradle movement.
- Lower jack slowly until crossmember contacts body bolt retainers. As jack is being lowered, correct any interferences between brackets, hoses, pipes, and wiring harnesses. NOTE: Lowering cradle without it being restrained could cause damage to body and underhood components.
- Remove outer blower case-to-cowl screws, and remove blower and case assembly. Remove evaporator. To install, reverse removal procedure.
HEATER CORE
Note. Heater core and evaporator core removal are covered in one procedure for some models. Refer to Evaporator and Heater Core later in this article.
- Drain cooling system. Remove heater hoses from heater core. Remove right-hand lower hush panel and right-hand lower trim of instrument panel. Remove lower right-hand instrument carrier-to-cowl screw.
- Remove 4 heater case cover screws. (Scheme 6) Upper left-hand screw is reached, using a long socket extension through panel opening. Lift corner of instrument panel slightly to align socket. Remove heater case cover.
- Remove core support plate and baffle screws. Remove heater core, support plate, and baffle. To install, reverse removal procedure. Seal any air leaks, and check for coolant leakage.
Heater Case and Core Assembly Camaro and Firebird models are illustrated. Scheme 6
Replacement (Chevette)
Disconnect battery. Disconnect refrigerant hose bracket from heater core cover. Disconnect and plug heater hoses and core pipes. Remove screws from heater core cover. Remove cover and core. To install, reverse removal procedure.
- Disconnect battery ground cable, and drain coolant. Disconnect hoses from heater core. Working inside vehicle, remove instrument panel trim covers, and lower steering column. Remove instrument cluster and front speakers.
- Remove 10 screws securing panel to heater case and cowl. Disconnect wiring harness, brake release cable, mirror cable, speedometer cable, and other wiring. Remove instrument panel.
- Remove defroster ducts and blower resistor assembly. Remove nuts securing heater assembly to firewall (reach 1 through blower resistor opening). Remove heater assembly and core. To install, reverse removal procedure.
Replacement ("X" Bodies)
- Drain cooling system, and remove hoses from heater core. Disconnect battery ground cable. Working inside vehicle, remove instrument panel sound absorber (if equipped), instrument cluster, glove box, radio, heater-A/C control, headlamp switch, and ash tray housing.
- Lower steering column. Remove 4 screws attaching instrument panel to cowl ledge and screws at either end of dash. Remove nut securing column bracket to panel. Remove electrical connections and parking brake release assembly.
- Remove instrument panel with wiring harness. Remove duct screws, left speaker, and duct assembly. Remove heater case side cover and heater core. To install, reverse removal procedure.
Replacement ("A" Bodies)
- Drain cooling system. On diesel V6 models, raise vehicle. Disconnect hoses on all models. On diesel V6 models, remove instrument panel sound absorber.
- On all models, remove heater duct and heater case side covers. Remove heater lower outlet. Remove 2 housing cover-to-air valve housing clips. Remove cover, core straps, tubing retainers, and heater core. To install, reverse removal procedure.
- Disconnect battery ground cable. If removing evaporator, discharge refrigerant system using approved refrigerant recovery/recycling equipment. Drain cooling system if removing heater core. Disconnect all electrical connections from blower motor, resistor, sensing switch, and relay. Remove right-hand windshield wiper arm.
- Remove rubber seal and module air intake screen. Remove module top cover screws and bolts. Remove cover. To remove heater core, lift out of case. To remove evaporator core, remove accumulator bracket screws. Disconnect refrigerant lines, and remove core from case. see scheme 7
- To install, reverse removal procedure. Add 3 oz. new refrigerant oil to evaporator core. Apply new sealant along edges of module cover to prevent water leaks. Evacuate and charge system.
- Disconnect battery ground cable, and drain cooling system. If removing evaporator, discharge system using approved refrigerant recovery/recycling equipment. Raise vehicle, remove drain tube from heater case, and disconnect heater hoses (and evaporator lines) from core.
- Lower vehicle, and remove left-hand and right-hand hush panels, steering column trim cover, heater outlet duct, and glove box.
- Remove heater core cover, pulling straight rearward to avoid breaking drain tube. Remove heater core clamps and core. Remove defroster vacuum actuator from case. Remove evaporator cover and core.
- To install, reverse removal procedure. Evacuate A/C system and fill cooling system.
Disconnect battery ground cable and blower motor wiring. Scribe blower motor flange-to-case position, and remove screws. Pry motor flange gently to remove motor. To install, reverse removal procedure.
Remove screw from control head bezel. Remove radio knobs, and remove bezel. Remove control head screws. Disconnect wiring, vacuum hoses, and cable. Remove control head. To install, reverse removal procedure.
Replacement (Corvette)
Disconnect battery ground cable. Remove floor console trim plate and side panels. Disconnect cables, vacuum lines, and wiring. Remove control head. To install, reverse removal procedure
Replacement ("A" & "X" Bodies)
Disconnect battery ground cable. Disconnect temperature control cable. Remove control screws, pull out control head, and disconnect wiring and vacuum lines. To install, reverse removal procedure.
Replacement (Camaro, Firebird, Riviera & Toronado)
Disconnect battery ground cable. Remove trim plate. Remove mounting screws, pull control head out, and disconnect vacuum and electrical connections. Remove control head. To install, reverse removal procedures.
- Disconnect battery ground cable. Remove ash tray and housing, trim panels and glove box. Disconnect temperature cable at A/C heater module.
- Remove screws from control head, and pull control out. Disconnect vacuum lines, wiring, and temperature cable. Remove control head. Reverse removal procedure to install.
- Disconnect battery ground cable. Remove steering column cover. Remove right-hand trim cover. Remove screws attaching control head to instrument panel.
- Pull control head out far enough to remove cables, electrical connectors, and vacuum lines. Remove control head. To install, reverse removal procedure.
When removing high pressure switch, system must be discharged using approved refrigerant recovery/recycling equipment. All other switches are on Schrader-type valves, and do not require system discharge.
