Trooper LS V6-3.5L (1998)
A/C Signal: Description and Operation
A/C Request Signal
This signal tells the PCM when the A/C mode is selected at the A/C control head. The PCM uses this to adjust the idle speed before turning on the A/C
clutch. The A/C compressor will be inoperative if this signal is not available to the PCM.
Refer to A/C Clutch Circuit Diagnosis for A/C wiring diagrams and diagnosis for A/C electrical system.
A/C Clutch Circuit Purpose
The A/C compressor operation is controlled by the powertrain control module (PCM) for the following reasons:
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It improvises idle quality during compressor clutch engagement.
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It improvises wide open throttle (WOT) performance.
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It 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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The A/C control head.
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The A/C refrigerant pressure switches.
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The A/C compressor clutch.
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The A/C compressor clutch relay.
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The PCM.
A/C Clutch Circuit Operation
A 12-volt signal is supplied to the A/C request input of the PCM when the A/C is selected through the A/C control switch.
The A/C compressor clutch relay is controlled through the PCM. This allows the PCM to modify the idle air control position prior to the A/C clutch
engagement for better idle quality. If the engine operating conditions are within their specified calibrated acceptable ranges, the PCM will enable the
A/C compressor relay. This is done 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. The PCM will not enable the A/C compressor clutch if any of the following conditions are met:
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The throttle is greater than 90%.
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The engine speed is greater than 6315 RPM.
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The ECT is greater than 119°C (246°F).
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The IAT is less than 5°C (41°F).
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The throttle is more than 80% open.
