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CONTROLSA/C COMPRESSOR CLUTCH
The compressor clutch assembly consists of a stationary electromagnetic coil, a rotor bearing and rotor assembly and a clutch plate. The electromagnetic coil unit and the rotor bearing and rotor assembly are each retained on the nose of the compressor front housing with snap rings. The clutch plate is keyed to the compressor shaft and secured with a nut. These components provide the means to engage and disengage the compressor from the engine serpentine accessory drive belt.
When the clutch coil is energized, it magnetically draws the clutch into contact with the rotor and drives the compressor shaft. When the coil is not energized, the rotor freewheels on the clutch rotor bearing, which is part of the rotor. The compressor clutch and coil are the only serviced parts on the compressor.
The compressor clutch engagement is controlled by several components: the A/C Heater mode control switch, the A/C high pressure transducer, the compressor clutch relay, and the (JTEC). The JTEC may delay compressor clutch engagement for up to thirty seconds. Refer to Electronic Control Modules for more information on the JTEC controls.
COMPRESSOR CLUTCH RELAY
The compressor clutch relay is a International Standards Organization (ISO) micro-relay. The terminal designations and functions are the same as a conventional ISO relay. However, the micro-relay terminal orientation (footprint) is different, the current capacity is lower, and the relay case dimensions are smaller than those of the conventional ISO relay.
The compressor clutch relay is located in the Power Distribution Center (PDC) in the engine compartment. Refer to the PDC label for relay identification and location.
The compressor clutch relay is a electromechanical device that switches battery current to the compressor clutch coil when the Powertrain Control Module (PCM) grounds the coil side of the relay. The PCM responds to inputs from the A/C Heater mode control switch, the A/C low pressure switch, and the A/C high pressure switch.
The compressor clutch relay cannot be repaired and, if faulty or damaged, it must be replaced.
A/C HEATER CONTROL
The A/C heater system uses a seriers of electrical controls These controls provide the vehicle operator with a number of setting options to help control the climate and comfort within the vehicle. Refer to the owner's manual in the vehicle glove box for more information on the features, use, and suggested operation of these controls.
The A/C heater control - (Single Zone) or (Dual Zone) panel is located to the right of the instrument cluster on the instrument panel.
The control panel contains a rotary-type temperature control, a rotary-type mode control switch knob, and a rotary-type blower motor speed switch knob. The control also has a push button to activate the Optional side view mirrors defroster elements and to turn the A/C ON.
The Dual Zone HVAC control panel contains a pair of slider-type temperature controls, a rotary-type mode control switch knob and a rotary-type blower motor speed switch knob. The control also has buttons to turn the A/C ON, Set it on Max A/C and for the Optional Heated Sideview Mirrors.
The A/C heater control panel cannot be repaired. If faulty or damaged, the entire unit must be replaced. The illumination lamps are available for service replacement.
A/C PRESSURE TRANSDUCER
The A/C pressure transducer is a switch that is installed on a fitting located on the refrigerant discharge line between the compressor and the condensor in the front corner of the engine compartment. An internally threaded hex fitting on the transducer connects it to the externally threaded Schrader-type fitting on the liquid line. A rubber O-ring seals the connection between the transducer and the discharge line fitting. Three terminals within a molded plastic connector receptacle on the top of the transducer connect it to the vehicle electrical system through a take out and connector of the headlamp and dash wire harness.
The A/C pressure transducer cannot be adjusted or repaired and, if faulty or damaged, it musty be replaced.
The A/C pressure transducer monitors the pressures in the high side of the refrigerant system through its connection to a fitting on the discharge line. The transducer will change its internal resistance in response to the pressures it monitors. The Powertrain Control Module (PCM) provides a five volt reference signal and a sensor ground to the transducer, then monitors the output voltage of the transducer on a sensor return circuit to determine refrigerant pressure. The PCM is programmed to respond to this and other sensor inputs by controlling the operation of the air conditioning compressor clutch and the radiator cooling fan to help optimize air conditioning system performance and to protect the system components from damage. The A/C pressure transducer input to the PCM will also prevent the air conditioning compressor clutch from engaging when ambient temperatures are below about 10 ° C due to the pressure/temperature relationship of the refrigerant. The Schrader-type valve in the discharge line fitting permits the A/C pressure transducer to be removed or installed without disturbing the refrigerant in the system. The A/C pressure transducer is diagnosed using a DRB III scan tool. Refer to the appropriate diagnostic information.