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A/c Compressor Clutch Controls Chevrolet Caprice Impala SS

A/c Compressor 3 illustrations ~616 words

MODEL IDENTIFICATION

Body Designation (1)Model
"B" BodyCaprice, Impala SS & Roadmaster
(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 A/C COMPRESSOR CLUTCH RELAY LOCATION table for A/C compressor clutch relay location.

RELAY LOCATION

ApplicationLocation
"B" BodyIn Fuse/Relay Block, On Right Rear Of Engine Compartment

A/C COMPRESSOR CLUTCH RELAY LOCATION

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 4.3L - VIN W - 5.7L - VIN P

Powertrain Control Module (PCM) delays A/C compressor clutch engagement momentarily after A/C is turned on. This delay allows PCM time to adjust engine RPM before A/C compressor clutch engages.

PCM will temporarily disengage A/C compressor clutch for a precalibrated time during one or more of the following conditions: Wide Open Throttle (WOT), high engine RPM, high engine coolant temperature, or A/C refrigerant pressure too high or too low.

An A/C refrigerant pressure sensor is used to monitor A/C system pressure. If A/C refrigerant pressure is greater than 429 psi (30.2 kg/cm 2 ) or less than zero, A/C compressor clutch will not engage. If A/C refrigerant pressure sensor signal wire becomes open, shorted to ground or shorted to voltage, Diagnostic Trouble Code (DTC) 66 will set.

If A/C compressor clutch engages and no refrigerant pressure change is detected, DTC 67 will set. When A/C request is detected by PCM, cooling fan(s) will be turned on unless vehicle speed is too fast.

Scheme 1

Scheme 1: CHART C-10 - A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS 4.3L - VIN W - 5.7L - VIN P
Scheme 1: CHART C-10 - A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS 4.3L - VIN W - 5.7L - VIN P

Note. Test numbers refer to numbers on diagnostic chart. (Scheme 2)and (Scheme 3).

1) Checks PCM's ability to control A/C compressor clutch relay.

2) Before replacing A/C system control components, refer to the appropriate A/C-HEATER SYSTEM article in the AIR CONDITIONING & HEAT section. See A/C-HEATER SYSTEM - Caprice, Impala SS or A/C-HEATER SYSTEM - MANUAL - Roadmaster.

3) Checks for a grounded circuit No. 459 to PCM.

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3
Scheme 3

Diagnostic Aids

Before diagnosing vehicle using C-10 chart, ensure no DTCs are stored. PCM will not activate A/C compressor clutch if any DTC is stored.