Audi Workshop Service and Repair Manuals

Functions

• ◆ → The low/high pressure switch (switch between contacts 1 and 2) deactivates the compressor in the event of a vacuum or overpressure in the refrigerant circuit (via the operating and display unit -E87).

• ‒ Switching pressures (overpressure in bar):
• ‒ Switch open (compressor off):
  Low pressure switch (opens at 1.2 bar and closes at 2.4 bar).
  High pressure switch (opens at 32 bar and closes at 24 bar).
• ‒ Switch closed (compressor on):
  between 1.2 (2.4) bar and 32 (24) bar.

• ◆ The high pressure switch (between contacts 3 and 4) switches radiator fan -V7 to speed 2.

• ‒ Switching pressures (overpressure in bar):
• ‒ Fan (speed 2) on (switch closes) at 16 bar.
• ‒ Fan (speed 2) off (switch opens) at 12.5 bar.

Removing and installing

• ‒ → Detach connector.
• ‒ Remove pressure switch -B-.
  Tightening torque: 5 Nm
• ‒ Replace O-ring seal -A- (10.8 mm; 1.8 mm) =>Page 87-22.

Notes:

• ‒ → Jumper contacts 1 and 2 of connector -B- in order to check refrigeration capacity with switch removed.
• ‒ The refrigerant circuit remains closed - connection with valve.

Check function.

• ‒ Start engine
• ‒ Compressor switched on (set "auto" mode on the operating and display unit).

• ‒ Compressor is driven:
• ‒ → Detach connector -B- from switch.
• ‒ Compressor stops (low pressure switch open).
• ‒ Remove switch -A- and connect connector -B-.
• ‒ Compressor is not switched on (low pressure switch open).
• ‒ Compressor is not driven:
• ‒ Detach connector -B- from switch -A- and jumper contacts 1 and 2 at connector -B- => compressor is switched on.

Notes:

• ◆ If the compressor is switched on when jumpered, either the refrigerant circuit pressure is too low (refrigerant circuit empty) or the switch is defective.
• ◆ To check the pressure in the refrigerant circuit, send the vehicle to an VW and Audi air-conditioning service centre.

• ◆ If the compressor is not switched on and the switch -F129 is displayed as a compressor shutoff criterion in the measured value block, locate and rectify the open circuit in the wiring between the switch -F129 and the -E87 =>Page 01-128.