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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 4 (Engine Controls - System/Component Tests) >> Miscellaneous ECM Controls >> Chart C-10, A/C Clutch Control Circuit Diagnosis (Rear A/C Only) (2 Of 2) 3.1L >> Diagnostic Aids

Diagnostic Aids

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If complaint was insufficient cooling, problem may be caused by inoperative cooling fan(s) or A/C refrigerant fan request switch. Engine cooling fan(s) should turn on when A/C pressure exceeds a value to open switch, which causes ECM to energize cooling fan relay(s). See CHART C-12 for cooling fan diagnosis. If fan operates correctly, ensure A/C system refrigerant charge is okay.

Fig 1: A/C Clutch Circuit Schematic (3.1L - Rear A/C Only)
G92I15881Courtesy of GENERAL MOTORS CORP.
Fig 2: A/C Clutch Circuit Flow Chart, (3.1L - Rear A/C Only)
G92A15917Courtesy of GENERAL MOTORS CORP.
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