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HOMESERVICE MANUALSCHEVROLET1994LUMINA BASEREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - SYSTEM/COMPONENT TESTS - 3.1LDIAGNOSTIC CHARTSCHART C-10, A/C COMPRESSOR CLUTCH CKT DIAG - VIN M (1 OF 2)NOTES
1994 Chevrolet Lumina Base

Chart C-10, A/C Compressor Clutch CKT Diag - VIN M (1 Of 2): Notes

1994 Chevrolet Lumina BaseSECTION Notes

A/C compressor clutch relay is controlled by the Powertrain Control Module (PCM). The PCM provides a ground on circuit No. 459 when 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/cm2 ) or greater than 429 psi (30.2 kg/cm2 ), or Diagnostic Trouble Code (DTC) 66 or 70 present and no A/C request signal exists from A/C select switch or circuit.

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. If DTCs are present, diagnose DTCs first. PCM will energize A/C 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.
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