SWITCH-A/C HIGH PRESSURE
DESCRIPTION
The A/C high pressure switch (1) sends a signal to the engine control module (ECM) to control A/C compressor clutch engagement/disengagement and, controls electric cooling fan operation when equipped with the 2.8L diesel engine. The A/C high pressure switch is mounted on a fitting located on the A/C discharge line near the A/C compressor. The ECM will disengage the A/C compressor clutch if the refrigerant system pressure exceeds 3100 - 3375 kPa (450 - 490 psi).
The fitting for the A/C high pressure switch on the A/C discharge line is equipped with an O-ring seal and contains a Schrader-type valve, which allows the switch to be serviced without discharging the refrigerant system.
OPERATION
The contacts in the A/C high pressure switch open and close causing the engine control module (ECM) to turn the A/C compressor clutch on and off. This prevents A/C compressor operation when the discharge pressure approaches high levels, and also reduces electrical surging from A/C clutch engagement.
The A/C high pressure switch controls the electric cooling fan operation by monitoring refrigerant line pressures. When the A/C discharge line pressure rises above 1900 to 2200 kPa (280 to 320 psi) the fan will turn on. The cooling fan will turn off when the A/C discharge line pressure drops to 1600 kPa (235 psi).
The A/C high pressure switch contacts open when the A/C discharge line pressure rises above 3100 to 3375 kPa (450 to 490 psi). The A/C high pressure switch contacts close when the A/C discharge line pressure drops to 1860 to 2275 kPa (270 to 330 psi).
The A/C high pressure switch is factory-calibrated and cannot be adjusted or repaired and must be replaced if found inoperative or damaged.
REMOVAL
NOTE: It is not necessary to discharge the refrigerant system to replace the A/C high pressure switch.
NOTE: LHD model shown. RHD model similar.
1. Disconnect and isolate the negative battery cable.
2. Disconnect the wire harness connector (1) from the A/C high pressure switch (2) located on the A/C discharge line (3) near the A/C compressor (4).
3. Remove the A/C high pressure switch from the A/C discharge line and remove and discard the O-ring seal.
INSTALLATION
NOTE: Use only the specified O-ring as it is made of special material for R-134a. Use only refrigerant oil of the type required for the A/C compressor.
NOTE: LHD model shown. RHD model similar.
1. Lubricate a new rubber O-ring seal with clean refrigerant oil and install it on the A/C high pressure switch fitting.
2. Install the A/C high pressure switch (2) onto the A/C discharge line (3) near the A/C compressor (4). Hand-tightened the switch securely.
3. Connect the wire harness connector (1) to the A/C high pressure switch.
4. Reconnect the negative battery cable.