Checking A/C pressure switch -F129-: Functions

WARNING: This page does not describe the selected car, but rather 27 other vehicles, including the 2002 Volkswagen Cabrio, 2001 Volkswagen Cabrio, 2000 Volkswagen Cabrio, 1999 Volkswagen Jetta, and 1999 Volkswagen Golf. However, it is still accessible from the selected car via links, so may be relevant.

Switches A/C clutch -N25- OFF if system pressure is too low (low refrigerant charge). Switching occurs between terminals 1 (T4a/1) and 2 (T4a/2).

Switch opens (compressor OFF): below 1.2 bar (17.4 psi)
Switch closes (compressor ON): above 2.4 bar (34.8 psi)

Fig 1: Identifying Terminals Of A/C Pressure Switch F129
Courtesy of VOLKSWAGEN OF AMERICA, INC.

Switches A/C clutch -N25- OFF if system pressure is too high. Switching occurs between terminals 1 (T4a/1) and 2 (T4a/2).

Switch opens (compressor OFF): above 32.0 bar (464 psi)
Switch closes (compressor ON): below 24.0 bar (348 psi)

Switches coolant fan -V7- to second speed when A/C system pressure increases. Switching occurs between terminals 3 (T4a/3) and 4 (T4a/4).

Switch closes (2nd speed ON): above 16.0 bar (232 psi)
Switch opens (2nd speed OFF): below 12.5 bar (181.3 psi)
Switch identified with a green label or marked "R-134a"
To remove, unscrew switch from Schrader valve
Tightening torque: 8 N.m (71 in lb)