Durango 2WD V8-4.7L Flex Fuel (2009)
Refrigerant Pressure Sensor / Switch: Description and Operation
Front A/C Pressure Transducer - Operation
OPERATION
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
A/C pressure transducer will change its internal resistance in response to the pressures it monitors. A 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 A/C system.
On gasoline engine models, the Front Control Module (FCM) provides a five volt reference signal to the A/C pressure transducer, then monitors the
output voltage of the A/C pressure transducer on a sensor return circuit to determine refrigerant pressure. The FCM broadcasts a refrigerant pressure
message to the Powertrain Control Module (PCM), which is programmed to respond to the A/C pressure transducer and other sensor inputs by
controlling the operation of the A/C compressor clutch and the radiator cooling fan to help optimize A/C system performance and to protect the system
components from damage. The PCM will disengage the A/C compressor clutch when high side pressure rises above 3275 kPa (475 psi) and re-engage
the clutch when high side pressure drops below 1999 kPa (290 psi). The A/C pressure transducer will also disengage the A/C compressor clutch if the
high side pressure drops below 193 kPa (28 psi) and will re-engage the clutch when the high side pressure rises above 234 kPa (34 psi). If the refrigerant
pressure rises above 1655 kPa (240 psi), the PCM will actuate the cooling fan. The A/C pressure transducer message to the PCM will also prevent the
A/C compressor clutch from engaging when ambient temperatures are below about 4.5° C (40° F) due to the pressure/temperature relationship of the
refrigerant. See Electric A/C Condenser Cooling Fan Switch Point charts for condenser cooling fan on/off pressures.
On Hybrid Electric Vehicle (HEV) models, the A/C-heater control receives the A/C pressure transducer signal from the FCM. The A/C-heater control
will then do the following based on head pressure:
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<= 2.0 Bar (29 psi) Disable compressor for low charge
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> 2.5 Bar (36 psi) Enable compressor
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>= 28 Bar (406 psi) Reduce compressor speed to reduce head pressure
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>= 29.5 Bar (427 psi) Shut down compressor due to high head pressure
-
< 21 Bar (306 psi) Re-enable compressor if previously shut down
The A/C pressure transducer is diagnosed using a scan tool See: Powertrain Management/Computers and Control Systems/Testing and
Inspection/Diagnostic Trouble Code Tests and Associated Procedures.
The A/C pressure transducer cannot be adjusted or repaired and must be replaced if inoperative or damaged.
ELECTRIC A/C CONDENSER COOLING FAN SWITCH POINT - 3.7L/4.7L/5.7L GAS ENGINES
ELECTRIC A/C CONDENSER COOLING FAN SWITCH POINT - 5.7L HEV ENGINE
