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Series II V8 Aircon high & low pressure switch locations

BassCoaster

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Hi all, a few weeks ago my aircon stopped dead. Had a closer look and the compressor isn't engaging. VE SII Calais V 6.0L.

Took to to an aircon place to check the pressure & re-gas if necessary and there was plenty of pressure.

I checked fuses and relays, all ok and I've never had an over pressure issue like some forum members seem to have had.

It's a 2011, MY12 and has 170,000 highway km on the clock. My guess is age or bugs have caused one of the switches to pack up. I need to find which one it is and replace it. Air con guy agrees that it's most likely the low pressure switch.

Before I put it up on the ramps I'd like to know where to start looking?
 

Dime

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Hey mate I have this issue now, did you end up figuring out what the problem was?
 

BlackVXGTS

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You replied to a very old post, but the items below may help you get an answer. Note that the aircon guy referred to in the post didn't seem to understand the VE A/C system.

A/C Pressure Sensor

The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuits enable the sensor to operate. The A/C pressure signal can be between 0-5 volts. When the A/C refrigerant pressure is low, the signal value is near 0 volts. When the A/C refrigerant pressure is high, the signal value is near 5 volts. The engine control module (ECM) converts the voltage signal to a pressure value.

It provides a 0-5 volt output and requires a 5-volt regulated power supply. In operation, the transducer senses applied pressure via the deflection of a 2 piece ceramic diaphragm with one half being a parallel plate capacitor. Changes in capacitance influenced by the refrigerant pressure under the ceramic diaphragm are converted to an analogue output by the transducers integral signal electronics. The pressure transducer's electronics are on a flexible circuit board contained in the upper section of the transducer. They provide linear calibration of the capacitance signal from the ceramic sensing diaphragm. Benefits of using the pressure transducer over a normal type pressure switch is that the transducer is constantly monitoring pressures and sending signals to the ECM. The normal type pressure switch only has an upper and lower cut out point. The ECM will disengage the A/C compressor at low or high refrigerant pressures and electronic diagnostic equipment can be used to extract system pressure information making it easier when diagnosing concerns. As well as acting as an input to the ECM for A/C operation, the ECM also uses the information provided by the pressure transducer to determine when to turn ON and OFF the 2nd Stage cooling fan operation.
 

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  • Air Conditioning (AC) Refrigerant Pressure Sensor Replacement.pdf
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