New Beetle GLS L4-2.0L (AZG) (2002)
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F129 has three functions:
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Switches the A/C clutch N25 off (via J293) when excessive refrigerant circuit pressure is present (e.g.: insufficient air flow over condenser or
when overcharged).
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Switches the A/C clutch N25 off (via J293) when insufficient refrigerant circuit pressure is present (e.g.: when refrigerant has leaked out)
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Switches on the second speed coolant fan V7 when refrigerant circuit pressure increases (approx. 16 bar).
Note:
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The presence of F129 is engine dependant. Where F129 is not used, high pressure sensor G65 is used instead.
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Always confirm system use of either F129 or G65 and applicable wiring circuit using applicable "Engine" and "Air conditioning" wiring diagrams.
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A/C Pressure Switch F129 replaces the A/C Refrigerant High Pressure Switch F23, A/C Refrigerant Low Pressure Switch F73 and the A/C
Refrigerant High Pressure Switch F118.
High Pressure Sensor G65
Where equipped, the High Pressure Sensor G65 transmits a square wave signal to Coolant Fan Control (FC) Module J293 at a rate which varies
according to the refrigerant system pressure.
The signal from High Pressure Sensor G65 is processed as follows:
Based on the pulse rate transmitted by the High Pressure Sensor G65, the Coolant Fan Control (FC) Module J293 determines the A/C refrigerant
system pressure and controls the function of the A/C Clutch N25 and Coolant Fans accordingly. For example:
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Switches the Coolant Fan V7 to the next higher speed when pressure in the refrigerant circuit increases.
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Switches off A/C Clutch N25 when pressure is excessive (for example when engine cooling is insufficient).
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Switches off A/C Clutch N25 off when pressure is too low (for example with low/no refrigerant).
The signal generated by High Pressure Sensor G65 is also provided as an input to the Motronic Engine Control Module (ECM). As the amount of
torque needed to drive the A/C compressor varies according to the refrigerant system pressure, the ECM processes this signal in order to enhance
engine performance.
Note:
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The presence of G65 is engine dependant. Where G65 is not used, A/C pressure switch F129 is used instead.
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Where G65 is used, its wiring circuit varies according to engine application (E.g.: some are connected to the ECM, some are not).
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Always confirm system use of G65 and applicable wiring circuit using applicable "Engine" and "Air conditioning" wiring diagrams.