A/C Pressure Switch -F129

A/C Pressure Switch -F129-, Checking


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 10,8 mm x 1,8 mm 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).


-F129- 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 condenser is blocked), -F129- switches A/C clutch off.