A/C Pressure Sensor/Switch - Cooling Fan: Testing and Inspection

A/C Pressure Switch F129, electrical checking

Note:
- Before carrying out any works on the A/C refrigerant system, refer to A/C system safety measures WARNINGS! and CAUTIONS!
- 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.

Function






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 (FC) 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).

Quick check






- With engine running, disconnect electrical connector from switch and briefly bridge connector terminals -1- and -2-. If the A/C Clutch N25 engages, the refrigerant circuit is empty.

A/C Pressure Switch F129, functional checks

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

- Check refrigerant capacity (fill). If system pressure is too low (refrigerant leakage), A/C Pressure Switch F129 switches A/C Clutch N25 off.
- Check cooling fan function. When system pressure increases, A/C Pressure Switch 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), A/C Pressure Switch F129 switches A/C Clutch N25 off.