A/C Pressure Switch F129

A/C Pressure Switch, Electrical Checks

Note:
- The presence of F129 is engine dependant. Where F129 is not used, high pressure sensor G65 is used instead.
- Always confirm system use of either F129 or G65 and applicable wiring circuit using applicable "Engine" and "Air conditioning" wiring diagrams.

The pressure switch can be removed without discharging refrigerant system.

- Visually check that O-ring 10.8mm x 1.8mm is positioned correctly in the groove.






Switch part between terminals 1 and 2 switches off the A/C clutch -N25- when the system pressure is too high or when there is not enough refrigerant in the system.

- Switch opens when the pressure is below 1.2 bar and closes again above 2.4 bar (switch point).
- Switch opens above 32 bar and closes again below 24 bar (switch point).

Switch part between terminals 3 and 4 switches coolant fan V7 (via the coolant fan control module J293 ) to the next higher fan speed when system pressures increase.

- Switch closes above 16 bar and opens again below 12.5 bar (switch point).

A/C Pressure Switch, Functional Checks

To determine proper A/C system performance, perform the following functional checks with the switch installed and connected.

- With the engine running, briefly bridge terminal 1 and 2 of connector. If the A/C clutch N25 engages, the refrigerant circuit is empty.
- Check refrigerant capacity (fill). If system pressure is too low (refrigerant leakage), F129 switches A/C clutch off.
- Check cooling fan function. When system pressure increases, F129 causes coolant fan V7 to switch to next higher fan speed.
- Check if A/C system switches off. At excessive system pressures (e.g.: caused by high ambient temperatures or if condensor is blocked), F129 switches A/C clutch off.