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Home >> Geo >> 1995 >> Metro Base, 2D Hatchback >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests - 1.0L 3-CYL >> Diagnostic Charts >> Chart C-1B, A/C Idle-Up Circuit Check >> Notes

Chart C-1B, A/C Idle-Up Circuit Check: Notes

When the A/C compressor clutch is in operation, the A/C amplifier will send an A/C idle-up signal to the ECM. ECM signals the ISC motor which activates a plunger to open the throttle plate. When throttle plate opens, engine idle speed increases preventing rough idle or stalling.

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. Checks to see if engine idle speed increases with A/C operation.
  2. Checks for a faulty A/C amplifier. This also checks for an open or short to ground or a short to voltage in Blue/Red wire.
  3. Checks for an open, a short to ground or a short to voltage in Light Green/Red wire or for a faulty ECM.
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