Camaro V6-3.8L VIN K (1995)
A/C Signal: Description and Operation
DESCRIPTION
The air conditioning system uses a compressor with variable displacement. This compressor is referred to as the V-5 type compressor The V-5
compressor meets A/C requirements without cycling.
The A/C compressor operation is controlled by the Powertrain Control Module (PCM) for the following reasons:
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Improves idle quality during compressor clutch engagement.
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Improves wide open throttle performance (WOT).
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Provides A/C compressor protection from operation with incorrect refrigerant pressures
The A/C electrical system consists of the following components:
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A/C control head.
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A/C refrigerant pressure switch.
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A/C compressor clutch.
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A/C compressor clutch relay.
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PCM.
OPERATION
When A/C is selected through the A/C control head a 12 volt signal is supplied to the A/C request input of the PCM. The A/C compressor clutch
relay is controlled through the PCM. This allows the PCM to increase the engine idle speed just prior to A/C clutch engagement for better idle
quality. In addition the PCM will command the cooling fans on during A/C operation. The PCM monitors the A/C refrigerant pressure. If the A/C
refrigerant pressure, and engine operating conditions are within a specific calibrated acceptable ranges the PCM will enable the A/C compressor
relay. This is accomplished by providing a ground path for the A/C relay coil within the PCM. When the A/C compressor relay is enabled battery
voltage is supplied to the compressor clutch coil.
The PCM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested, unless any of the following
conditions are met:
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Throttle greater than 90%.
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A/C head pressure greater than 414 psi or less than 34 psi (as determined by the A/C refrigerant pressure sensor).
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Ignition voltage below 10.5 volts.
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Engine speed greater than 4500 RPM for 5 seconds or 5400 RPM.
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Engine Coolant Temperature (ECT) greater than 125°C (257°F).
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Intake Air Temperature (IAT) less than 5°C (41°F).
