Checking A/C pressure switch -F129-: Functions

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)