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A/c Compressor Clutch Controls Buick Skylark VII

A/c Compressor 7 illustrations ~1066 words

MODEL IDENTIFICATION

Body Designation (1)Model
"N" BodyAchieva, Grand Am & Skylark
(1) Body codes determined by fourth character of VIN code.
(1)Body codes determined by fourth character of VIN code.

BODY CODE DESIGNATIONS

DESCRIPTION & OPERATION

To improve idle quality and Wide Open Throttle (WOT) performance, and for system protection, the A/C compressor clutch is controlled by the Powertrain Control Module (PCM).

A refrigerant pressure sensor is used to indicate high and low side refrigerant pressure to the PCM for controlling cooling fan, A/C compressor clutch and Idle Air Control (IAC) valve. If a fault is detected in refrigerant pressure circuit, A/C compressor clutch will be disabled.

The A/C compressor clutch relay is controlled by the PCM. This allows the PCM to raise idle speed before engaging compressor clutch, and disable compressor clutch during WOT, high engine RPM, high power steering loads and hot engine restarts. PCM also disables compressor clutch if coolant temperature becomes excessive.

TROUBLE SHOOTING

Note. This article contains test charts which are part of General Motors Computerized Engine Controls. Only those charts required to test A/C compressor clutch control are included. Other diagnostic information may be referenced while performing A/C compressor clutch control diagnosis. For complete information on General Motors Computerized Engine Control systems, see the appropriate G-TESTS W/CODES article in the ENGINE PERFORMANCE section.

Trouble shoot A/C compressor clutch control using appropriate schematic and diagnostic charts. See TROUBLE SHOOTING CHART DIRECTORY. See A/C COMPRESSOR CLUTCH RELAY LOCATION table for A/C compressor clutch relay location.

RELAY LOCATION

ApplicationLocation
"N" Body(1) On Right Rear Corner Of Engine Compartment
(1) (Scheme 1)

A/C COMPRESSOR CLUTCH RELAY LOCATION

Scheme 1

Scheme 1
Scheme 1

TROUBLE SHOOTING CHART DIRECTORY

ApplicationSee Figure
2.3L VIN DFigs. (Scheme 2) -4
3.1L VIN MFigs. (Scheme 5) -7

A/C COMPRESSOR CLUTCH CHART INDEX

SCAN TESTER

A variety of information is transmitted through Data Link Connector (DLC) terminal "E" or "M", depending on engine. This data is transmitted at a high frequency which requires a Tech 1 scan tester for interpretation. Several scan testers are available for diagnostic work. Scan testers other than Tech 1 scan tester will function and provide information for diagnostic work; however, some charts will specify a Tech 1 scan tester. Failure to use a Tech 1 scan tester when specified may result in incorrect diagnosis of a system.

CHART C-10 - A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS 2.3L - VIN D

A/C compressor clutch relay is controlled by the Powertrain Control Module (PCM). The PCM provides a ground on circuit No. 459 and A/C is requested. PCM will delay A/C compressor clutch engagement momentarily after A/C is requested. This delay allows Idle Air Control (IAC) valve to adjust engine RPM for additional load.

PCM will temporarily disengage A/C compressor clutch for a precalibrated time during one or more of the following conditions: hot engine restart, Wide Open Throttle (WOT), engine RPM greater than 6000 RPM and IAC reset. A/C compressor clutch will remain disengaged if Diagnostic Trouble Code (DTC) 66 is present, refrigerant pressure is too low or high, and no A/C request signal exists from A/C select switch or circuit.

Scheme 2

Scheme 2: CHART C-10 - A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS 2.3L - VIN D
Scheme 2: CHART C-10 - A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS 2.3L - VIN D

Note. Test numbers refer to numbers on diagnostic chart. (Scheme 3)

1) If DTCs are present, see the appropriate G-TESTS W/CODES article in the ENGINE PERFORMANCE section.

PCM will energize A/C compressor clutch relay only when engine is running. This test determines whether relay or circuit No. 459 is faulty.

2) Determines if signal is reaching PCM through circuit No. 66 from A/C control panel. Signal should only be present when A/C mode or defrost mode is selected.

Scheme 3

Scheme 3
Scheme 3

Note. Test numbers refer to numbers on diagnostic chart. (Scheme 4)

1) Determines if A/C pressure sensor is out-of-range, causing A/C compressor clutch to be disengaged.

2) With engine off and field service mode activated, PCM should ground circuit No. 459, causing test light to come on.

Scheme 4

Scheme 4
Scheme 4

Diagnostic Aids

If complaint is insufficient cooling, problem may be caused by an inoperative cooling fan. See appropriate C-12 chart in the ENGINE COOLING FAN article in the ENGINE COOLING section. If cooling fan operates correctly, problem is a basic A/C system problem.

PCM will disable A/C compressor if refrigerant pressure is not 43-428 psi (3.0-30.1 kg/cm 2 ). If refrigerant pressure is okay, check A/C pressure sensor circuit. If A/C pressure sensor circuit is okay, replace A/C pressure sensor.

CHART C-10 - A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS 3.1L - VIN M

A/C compressor clutch relay is controlled by the Powertrain Control Module (PCM). The PCM provides a ground on circuit No. 459 and A/C is requested. PCM will delay A/C compressor clutch engagement momentarily after A/C is requested. This delay allows Idle Air Control (IAC) valve to adjust engine RPM for additional load.

PCM will temporarily disengage A/C compressor clutch for a precalibrated time during one or more of the following conditions: engine not running, engine coolant temperature greater than 255°F (124°C), A/C refrigerant pressure less than 38 psi (2.7 kg/cm 2 ) or greater than 429 psi (30.2 kg/cm 2 ), or if Diagnostic Trouble Code (DTC) 66 or 70 is present and no A/C request signal exists from A/C select switch or circuit.

Scheme 5

Scheme 5: CHART C-10 - A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS 3.1L - VIN M
Scheme 5: CHART C-10 - A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS 3.1L - VIN M

Note. Test numbers refer to numbers on diagnostic chart. (Scheme 6)

1) If DTCs are present, see the appropriate G-TESTS W/CODES article in the ENGINE PERFORMANCE section.

PCM will energize A/C relay only when engine is running. Determines whether relay or circuit No. 459 is faulty.

2) Determines if signal is reaching PCM through circuit No. 66 from A/C control panel. Signal should only be present when A/C mode or defrost mode is selected.

Scheme 6

Scheme 6
Scheme 6

Note. Test numbers refer to numbers on diagnostic chart. (Scheme 7)

1) Determines if A/C refrigerant pressure sensor is out-of-range, causing A/C compressor to be disengaged.

2) With engine off and A/C relay output test activated, PCM should be grounding circuit No. 459, causing test light to come on.

Scheme 7

Scheme 7
Scheme 7

Check branch circuits and splices to other components. If complaint is insufficient cooling, problem may be caused by an inoperative cooling fan. See appropriate C-12 chart in the ENGINE COOLING FAN article in the ENGINE COOLING section. If cooling fan operates correctly, problem is a basic A/C system problem.

PCM will disable A/C compressor if refrigerant pressure is not 38-429 psi (2.7-30.2 kg/cm 2 ). If refrigerant pressure is okay, check A/C pressure sensor circuit. If A/C pressure sensor circuit is okay, replace A/C pressure sensor.