A/c-Heater System - Manual Buick Century V

A/C SYSTEM SPECIFICATIONS

A/C SYSTEM SPECIFICATIONS

DESCRIPTION

Variable Displacement Orifice Tube (VDOT) refrigerant system uses a Harrison V5 5-cylinder variable displacement compressor. This system uses a fixed orifice tube to meter the flow of refrigerant into the evaporator. Basic compressor operation is achieved with a variable angle wobble plate and 5 axially oriented cylinders.

CONTROL PANEL

Several settings are possible on the control panel to provide desired comfort level. (Scheme 1) Mode settings will distribute air to appropriate outlets. (Scheme 2) Available mode settings are as follows

OFF

In this mode, blower operation and air conditioning do not take place. With vehicle forward movement, a slight amount of ram air will enter passenger compartment.

MAX

In this mode, maximum cooling is provided. Conditioned air is distributed through instrument panel outlets with a slight amount to floor outlets and defroster outlets.

NORM

In normal mode, conditioned air is distributed through instrument panel outlets with slight amount to floor and defroster outlets.

BI-LEV

In bi-level mode, conditioned air is distributed through instrument panel outlets with slight amount to floor and defroster outlets.

VENT

In this mode, the compressor does not operate. Outside air is delivered through instrument panel outlets.

In this mode, compressor does not operate. Outside air is heated and distributed: about 80 percent to floor outlets and 20 percent to defroster and side window defogger outlets.

DEF

In this mode, conditioned air is distributed: about 80 percent to defroster outlets and side window defogger outlets and 20 percent to floor outlets.

Scheme 1

Scheme 2

ACCUMULATOR

The accumulator is a refrigerant storing device, located at the evaporator outlet. This unit receives and stores vapor, some liquid and refrigerant oil from evaporator. An oil bleed hole is located in the lower portion of the accumulator, assuring return of the oil to the compressor. A bag of desiccant is located in the bottom of accumulator. (Scheme 3)

Scheme 3

A/C CONTROL RELAY

The Powertrain Control Module (PCM) energizes the A/C control relay for compressor operation. If the ECM receives a signal indicating Wide Open Throttle (WOT), excessive engine heat, low ambient temperature or low engine speed, ECM will de-energize A/C control relay, stopping compressor operation.

BLOWER RELAY

The blower relay is used to by-pass the blower motor resistor assembly for high speed blower operation. When blower switch is in the HI position, the blower relay is energized, applying direct battery voltage to blower motor.

HIGH PRESSURE CUT-OFF SWITCH

The high pressure cut-off switch stops compressor operation, preventing compressor damage and loss of refrigerant, if high side pressure exceeds about 430 psi (30 kg/cm 2 ). After pressure decreases to about 170 psi (11.9 kg/cm 2 ), compressor operation resumes.

ORIFICE TUBE

The orifice tube, located in evaporator inlet pipe, controls flow of liquid refrigerant into the evaporator. The orifice tube has filter screens on both inlet and outlet sides. When the engine is turned off with A/C operating, system refrigerant will flow from high pressure side of orifice tube to low pressure side until pressure is equalized. While pressure is equalizing, a faint hissing sound of liquid flowing may be heard for 30-60 seconds. This is a normal condition. The tube has no moving parts and is not adjustable. Replace tube if it is plugged or defective.

2.2L

Engine idle quality is maintained by cutting off power to A/C compressor when high power steering loads are present. The cut-off switch is normally open.

PRESSURE CYCLING SWITCH

Pressure cycling switch is located between compressor and condenser. Switch stops compressor operation if pressure is more than 430 psi (30 kg/cm 2 ) or less than 30 psi (2.1 kg/cm 2 ). This sensor is also used to boost idle speed for A/C operation and control cooling fan operation.

PRESSURE RELIEF VALVE

When discharge side pressure reaches about 440 psi (31 kg/cm 2 ), pressure relief valve, located on rear of compressor, opens automatically to prevent damage due to excessive pressure. Valve also opens if high pressure cut-off switch or electric cooling fan malfunctions.

WIDE OPEN THROTTLE (WOT) CUT-OUT SWITCH

The Throttle Position Sensor (TPS) opens a circuit to the compressor through the ECM during full acceleration.

TEMPERATURE CONTROL CABLE

Place temperature control lever in full COLD position. Loosen temperature control cable screw. Place loop of cable on heater case temperature door post. Push sheath toward heater door post until door seats and lash is out of cable. Tighten temperature control cable screw.

A/C COMPRESSOR CLUTCH CONTROL

Note. Also see A/C COMPRESSOR CLUTCH CONTROLS article

OPERATIONAL TESTING

When trouble shooting and diagnosing an air conditioning system, always refer to appropriate vacuum and wiring diagrams for the system involved. See VACUUM DIAGRAMS and WIRING DIAGRAMS .

If blower operates at all speeds and compressor clutch engages, electrical circuits are functioning properly. If evaporator inlet pipe and accumulator surface appear to be the same temperature when felt by hand, system is properly charged with refrigerant. Ensure vacuum and diaphragm function properly when moving selector control.

BLOWER MOTOR WILL NOT RUN

Check fuses. Turn ignition switch to RUN position. Check for voltage at function control switch. Switch blower switch to HI position. Check for voltage at switch and at high-speed blower relay. Ground blower motor with ignition switch in RUN position. If blower operates, motor is okay.

BLOWER DOES NOT OPERATE IN HI

Check for voltage at high-speed blower relay with ignition switch in RUN position and blower switch in HI position. If voltage is not present, check for voltage at blower switch.

BLOWER OPERATES ONLY IN HI

Check blower resistors for open condition. Check blower switch for voltage in each position.

BLOWER OPERATES IN HI WITH IGNITION OFF

Check blower motor relay.

A/C DOES NOT WORK

With engine running and function control switch at NORM position, check for voltage at pressure cycling switch. Check for voltage between pressure cycling switch and compressor clutch. Ground compressor clutch circuit. If clutch engages, check wide-open throttle cut-out switch and A/C compressor cut-off switch.

INSUFFICIENT COOLING

Note. QUICK CHECK procedure may be used to check for proper refrigerant charge in A/C system, provided ambient air temperature is more than 70°F (21°C). On vehicles with Cycling Clutch Orifice Tube (CCOT) system, compressor will cycle on and off to meet system requirements. CCOT system does not use a sight glass to check refrigerant charge.

Quick Check Procedure

1. Engine must be at normal operating temperature (not on fast idle or cold enrichment). Open vehicle doors and engine hood. Select NORM A/C position. Move temperature lever to COLD position. Turn blower switch to HI position. Engine should be at normal slow idle speed.
2. While compressor is engaged, feel temperature of accumulator surface and evaporator inlet pipe. If temperature of both components is the same (slightly cooler than ambient air), system is normal. If inlet pipe is frosted or feels cooler than accumulator surface, refrigerant charge is low.
3. Add refrigerant in 4-ounce increments, allowing system to stabilize between additions, until accumulator and pipe appear to be same temperature. Add 14 more ounces of refrigerant.

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

A/C COMPRESSOR CLUTCH DOES NOT ENGAGE

1. Remove A/C compressor control relay. Relay is located in engine compartment at relay bracket. Turn ignition switch to RUN position. Using a test light, backprobe both Pink wires of control relay. Test light should glow at both wires. If test light does not glow, repair open in Pink wires between control relay and fuse block.
2. If test light glowed in step 1), backprobe control relay between Pink and Dark Green wires. If test light glows, repair short to ground in Dark Green wire. If test light does not glow, attach a 15-amp fused jumper wire between Pink and Dark Green wires of A/C compressor control relay. Compressor clutch should engage.
3. If compressor clutch does not engage, check for poor connection or open circuit in Dark Green wire, or open circuit in compressor clutch ground wire. If wires and connections are good, replace A/C compressor clutch. If compressor clutch engages, reinstall control relay. Using a fused jumper wire, backprobe Dark Green/White wire of control relay. Compressor clutch should engage. If compressor clutch does not engage, replace A/C compressor control relay.
4. If compressor clutch engages, turn ignition to RUN position. Place mode select lever in MAX position. Using a test light, backprobe Light Green wire at A/C-heater control. If test light glows, go to next step. If test light does not glow, check for open in Light Green wire. If Light Green wire is good, check for open in Dark Green/White wire at A/C-heater control panel. If Dark Green/White wire is good, a check of the Powertrain Control Module (PCM) is required.
5. If test light glowed in step 4), backprobe Brown wire of A/C-heater control panel. If test light glows, repair open in Brown wire. If test light does not glow, check for poor connection at Brown wire. If connections are good, replace A/C-heater control panel.

A/C COMPRESSOR CLUTCH ALWAYS ENGAGED

1. Disconnect A/C-heater control wiring connector. Turn ignition switch to RUN position. If compressor clutch does not engage, replace A/C-heater control assembly. If compressor clutch engages, use a test light and backprobe Light Green wire between A/C-heater control and Powertrain Control Module (PCM). If test light glows, repair short to battery voltage in Light Green wire.
2. If test light does not glow, remove A/C-heater control relay. If compressor clutch engages, repair short to battery voltage in Dark Green wire between control relay and compressor clutch. If compressor clutch does not engage, check for short to ground in Dark Green/White wire between control relay and PCM. If circuit is good, check PCM. If PCM is good, replace A/C control relay.

BLOWER INOPERATIVE AT ANY SPEED

1. Check instrument panel fuse No. 12 (5-amp). Turn ignition switch to RUN position. Place mode select lever in VENT position. Turn blower switch to LO position. Using a test light, backprobe Purple wire of blower relay. Blower relay is located in engine compartment on relay bracket.
2. Test light should glow. If test light does not glow, go to next step. If test light glows, check for open circuit in Purple wire between blower relay and blower motor. Check for open circuit in Black wire between blower motor and ground. If all wires and connections are good, replace blower motor.
3. Disconnect blower relay. Backprobe Dark Blue wire of blower relay. Test light should glow. If test light glows, check for poor connections at blower relay. If connections are good, replace blower relay.
4. If test light does not glow, backprobe Brown wire at A/C-heater control panel. Test light should glow. If test light glows, check for open circuit in Brown wire between A/C-heater control panel and blower switch. If test light does not glow, backprobe Brown wire between A/C-heater control panel and fuse block.
5. If test light glows, replace A/C-heater control panel. If test light does not glow, check for open circuit in Brown wire between A/C-heater control panel and fuse block.

LOW SPEED INOPERATIVE, MEDIUM & HIGH SPEEDS OPERATE NORMALLY

1. Disconnect blower resistors. Turn ignition switch to RUN position. Place mode select lever in VENT position. Turn blower switch to LO position. Using a test light, backprobe Brown wire of blower resistor. Blower resistor is located in blower module.
2. Test light should glow. If test light does not glow, check for high resistance or open circuit in Brown wire between blower resistor and A/C-heater control unit.
3. If test light glows, check for poor connection at blower resistor connector. If connection is good, replace blower resistor.

MEDIUM SPEED(S) INOPERATIVE, LOW & HIGH SPEEDS OPERATE NORMALLY

1. Disconnect blower resistors. Turn ignition switch to RUN position. Place mode select lever in VENT position. Turn blower switch to medium-low position. Using a test light, backprobe Tan wire of blower resistor. Blower resistor is located in blower module.
2. Test light should glow. If test light glows, go to next step. If test light does not glow, check for poor connection or open in Tan wire between blower resistor and A/C-heater control panel.
3. Turn blower switch to medium-high position. Backprobe Light Blue wire of blower resistor. Test light should glow. If test light does not glow, go to next step. If test light glows, check for poor connection at blower resistor. If connection is good, replace blower resistor.
4. Check for open circuit and poor connection in Light Blue wire between blower resistor and A/C-heater control panel. If circuit and connections are good, replace A/C-heater control panel.

HIGH SPEED INOPERATIVE, LOW & MEDIUM SPEEDS OPERATE NORMALLY

1. Turn ignition switch to RUN position. Place mode select lever in VENT position. Turn blower switch to HI position. Using a test light, backprobe Orange wire of blower relay. Test light should glow. If test light glows, go to next step. If test light does not glow, go to step 3).
2. Backprobe Red wire of blower relay. Test light should glow. If test light glows, check for poor connection at blower relay and open circuit in Black wire between blower relay and ground. If circuits and connections are good, replace blower relay. If test light does not glow, repair open circuit in Red wire between blower relay and fusible link.
3. Check for open circuit and poor connection in Orange wire between blower switch and blower relay. If circuits and connections are good, replace A/C-heater control panel.

TESTING

A/C SYSTEM PERFORMANCE

1. Park vehicle out of direct sunlight. Connect tachometer. Install gauge set. Start engine. Turn A/C on. Place mode selection in NORM position, temperature lever on maximum cooling and blower switch in HI position.
2. Close doors and windows and open hood. Insert thermometer in center air outlet. Idle engine for 10 minutes. Measure temperature. Temperatures and pressures should be within correct range. See «A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/manual-hvac-system/#ac-heater-system-manual) and «A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/manual-hvac-system/#ac-heater-system-manual) tables.

A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS

A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS

AIR DELIVERY CONTROL TESTS

Before diagnosing vacuum actuators, check Black vacuum hoses and check valve between engine intake manifold tap and vacuum tank for damage. (Scheme 17) Repair hoses and valve as necessary. Check Violet vacuum hose between Black vacuum hose and control panel for damage. Repair hose as necessary. If hoses are okay, diagnose specific vacuum actuator.

A/C-Heater Valve Vacuum Actuator

1. A/C-heater valve vacuum actuator controls upper and lower mode valves. (Scheme 2) With A/C-heater mode lever in MAX, NORM or VENT position, vacuum is applied through Yellow vacuum hose. All air flows from instrument panel (vent) outlets.
2. Place A/C-heater mode lever in OFF, HEATER or DEF position. Vacuum is applied through Red vacuum hose to vacuum actuator. Air will flow from heater (floor) outlets, side window defogger outlets and defroster outlets.
3. With A/C-heater mode lever in BI-LEV (bi-level) position, vacuum is not applied to vacuum actuator. Air will flow from heater (floor) outlets and defroster outlets. If operation is not as described, repair vacuum hoses or replace A/C-heater valve vacuum actuator as necessary.

Defrost Valve Vacuum Actuator

Start engine. Vacuum is applied through Blue vacuum hose with A/C-heater mode lever in any position except DEF. Place A/C-heater mode lever in DEF position. Vacuum is not applied through Blue vacuum hose, causing defrost valve vacuum actuator to direct air to defroster outlets. If operation is not as described, repair vacuum hoses or replace defrost valve vacuum actuator as necessary.

Recirculating/Outside Valve Vacuum Actuator

1. Start engine. Place A/C-heater mode lever in MAX position. Vacuum is applied through Orange vacuum hose to recirculating/outside valve vacuum actuator, causing recirculating/outside valve to recirculate air inside vehicle.
2. With A/C-heater mode lever in any position except MAX, vacuum is not applied to recirculating/outside valve vacuum actuator, causing recirculating/outside valve to intake fresh air from outside vehicle. If operation is not as described, repair vacuum hoses or replace recirculating/outside valve vacuum actuator as necessary.

Temperature Valve

Valve is mechanically linked to A/C-heater control panel. When temperature control lever is in COLD position, air cannot flow across heater core. With temperature control lever in any position except COLD, air may flow across heater core. If operation is not as described, adjust, repair or replace temperature valve or control cable.

REMOVAL & INSTALLATION

Disconnect vacuum hose from actuator. Remove vacuum actuator nuts from A/C-heater module, and remove vacuum actuator. To install, reverse removal procedure.

1. Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. On 2.2L, remove air cleaner and resonator. On all models, disconnect and plug accumulator inlet and outlet lines. Loosen or remove accumulator bracket bolts. Remove accumulator with or without bracket as needed. Measure amount of refrigerant oil in old accumulator, and discard accumulator.
2. Add same amount of clean refrigerant oil as was drained from old accumulator. If no oil can be drained from old accumulator, add 3.5 ounces of new oil to new accumulator. To install, reverse removal procedure. Use new "O" rings lubricated with clean refrigerant oil. DO NOT soak "O" rings, as this will cause them to expand. Evacuate and recharge system.

Removal & Installation (2.2L)

Disconnect negative battery cable. Remove air cleaner and resonator assembly. Remove engine torque strut. Rotate engine forward. Disconnect blower motor connector. Remove vent tube. Remove blower motor screws. Remove blower motor from vehicle. To install, reverse removal procedure.

Removal & Installation (3.1L)

Disconnect negative battery cable. Drain cooling system. Remove drive belt. Remove generator bracket bolts and position generator aside. Disconnect blower motor connector. Remove vent tube. Remove blower motor screws. Remove blower motor from vehicle. To install, reverse removal procedure.

Locate blower motor resistor on blower motor case. Disconnect negative battery cable. Disconnect resistor wiring harness connector. Remove resistor screws, and remove resistor. To install, reverse removal procedure.

Removal

Discharge A/C system using approved refrigerant recovery/recycling equipment. Disconnect negative battery cable. On 2.2L, remove air cleaner and resonator. On all models, remove fitting block and hose assembly from rear of compressor. Remove compressor bracket bolts. Remove serpentine drive belt from A/C compressor. Remove compressor bolts. Raise and support vehicle. Remove compressor from vehicle.

Installation

1. To install, reverse removal procedure. Add same amount of clean refrigerant oil as was drained from compressor. If less than one ounce of oil was drained from compressor, add 2 ounces of new oil to compressor.
2. Use new "O" rings lubricated with clean refrigerant oil. DO NOT soak "O" rings, as this will cause them to expand. Install a new engine oil filter (if removed). Check engine oil level, and add oil as necessary. Evacuate and recharge system.

1. Remove A/C-heater control panel trim plate. Remove A/C-heater control panel-to-dashboard screws. Pull control panel rearward far enough to access vacuum and electrical connections.
2. Disconnect vacuum and electrical connections from control panel. Disconnect temperature control cable from control panel. Remove control panel from vehicle. To install, reverse removal procedure.

1. Disconnect negative battery cable. Remove 4 dashboard panel pad screws. Remove dashboard panel pad from top of dashboard assembly. Remove steering column filler panel. Remove one bolt to center brace. Remove top dashboard screws.
2. Loosen or remove lower dashboard screws as necessary. Carefully tilt dashboard rearward. Remove defroster ducts. Disconnect vacuum hose from actuator. Remove vacuum actuator from A/C-heater module. To install, reverse removal procedure.

1. Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Drain cooling system. Disconnect A/C-heater module electrical connections. Remove electrical harness straps from module. On 3.1L, remove throttle modulator assembly. On all models, remove heater hose routing bracket from cover. Remove liquid and low pressure lines from evaporator.
2. Remove resistor from top of blower motor cover. Disconnect blower motor connector. Remove blower motor cover screws. Remove evaporator core from vehicle. To install, reverse removal procedure. Evacuate and recharge system. Fill cooling system.

Disconnect negative battery cable. Drain engine coolant. Disconnect heater hoses at heater core. Remove lower instrument panel sound insulator. Remove floor outlet ducts. Remove heater core cover screws and clips. Remove heater core cover. Remove heater core from vehicle. To install heater core, reverse removal procedure. Fill cooling system.

Switches are mounted in-line at rear of compressor. Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove switch connector. Remove switch and "O" ring. To install, reverse removal procedure. Evacuate and recharge system.

Pressure cycling switch is mounted near accumulator. When removing pressure cycling switch, DO NOT discharge system. This sensor is on a Schrader-type valve. Disconnect connector. Remove switch from line. To install, reverse removal procedure.

Pressure relief valve is mounted in rear of compressor. Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove valve and "O" ring. To install, reverse removal procedure. Evacuate and recharge system.

1. Disconnect negative battery cable. Remove windshield wipers, lower windshield molding and cowl panel. Drilling no deeper than 5 mm, drill out 5 heat stakes using a drill with a 10-mm bit. Remove recirculating/outside air valve inlet housing top.
2. Disconnect vacuum hose from actuator. Disconnect actuator rod. Remove vacuum actuator nuts. Disengage actuator from valve, and remove actuator from vehicle. To install, reverse removal procedure.

Remove lower sound insulator from dashboard. Remove A/C-heater control panel. See CONTROL PANEL . Remove temperature control cable push nut retainer near A/C-heater module. Remove temperature control cable push nut retainer near control panel. Remove temperature control cable from vehicle. To install, reverse removal procedure.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Scheme 17

Manual A/C-Heater System Wiring Diagram (2.2L). Scheme 18

Manual A/C-Heater System Wiring Diagram (3.1L). Scheme 19

See also:
• VACUUM DIAGRAMS