Audi A4: A/C Pressure Switch -F129-
Note
Switch pressures, removing and installing switches as well
as switch arrangement and version. Refer to vehicle specific
refrigerant circuit
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; System
Overview - Refrigerant Circuit (vehicle-specific
repair manual).
This pressure switch has 3 functions:
1. Switches the coolant fan to the next higher level when
the pressure in the refrigerant circuit increases (approximately
16 bar (232 psi) ).
2. Switches off A/C system if pressure is excessive
(approximately 32 bar (464 psi) ), for example because of
insufficient engine cooling.
3. Switches off A/C system if pressure is insufficient
(approximately 2 bar (29 psi) ), for example loss of refrigerant.
Note
A/C Pressure Switch -F129- replaces the A/C Refrigerant High
Pressure Switch -F23-, A/C Refrigerant Low Pressure Switch -F73-
and the Magnetic Clutch High Pressure Switch -F118-.
High Pressure Sensor -G65-, Refrigerant Circuit Pressure Sensor -G805-
- This High Pressure Sensor -G65- is installed instead of the
A/C Pressure Switch -F129- or the A/C Pressure/Temperature
Sensor -G395-.
- The Refrigerant Circuit Pressure Sensor -G805- replaces the
High Pressure Sensor -G65- on specific vehicles from a specific
version and from a specific date of manufacture.
- When a voltage is applied, a version of the High Pressure
Sensor -G65- generates a square wave signal and the others a
data telegram. This signal changes along with pressure in the
system. When voltage is applied, the other versions and the
Refrigerant Circuit Pressure Sensor -G805- exchange information
with the Data bus (i.e. via the "LIN-Bus") with the
corresponding control module. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; System
Overview - Refrigerant Circuit (vehicle-specific
repair manual).
- On Audi A3 from MY 2005 and Audi Q3. a High Pressure Sensor
-G65- is installed, for example, which emits its measured values
to the corresponding control module (for example to the A/C
Control Module -J301- or the Climatronic Control Module -J255-).
On Audi Q7 from MY 2016, a High Pressure Sensor -G65- is
installed, for example, which sends its measured values via a
"LIN Bus". Use the Vehicle Diagnostic Tester ("OBD" function or
A/C system "Guided Fault Finding") and
→ Wiring diagrams, Troubleshooting & Component locations.
- The Refrigerant Circuit Pressure Sensor -G805- is installed
on the Audi A3 from MY 2013, for example. It exchanges
information with the corresponding control module (on Audi A3,
the A/C Control Module -J301- or the Climatronic Control Module
-J255-) via a data bus cable. Refer to
→ Wiring diagrams, Troubleshooting & Component locations
- The A/C Pressure/Temperature Sensor -G395-, the Refrigerant
Circuit Pressure Sensor -G805- and the High Pressure Sensor
-G65- are available in different versions. Currently the
sensor's only exterior difference is the parts number.
Therefore, make sure that the part numbers are correctly
allocated when replacing them (part number Parts Catalog ).
Reason: These sensors produce different signals that can only be
evaluated by the respective control modules using the
→ Vehicle Diagnostic Tester (function "OBD" or
"Guided Fault Finding" for the A/C system). Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; System
Overview - Refrigerant Circuit (vehicle-specific
repair manual).
- The High Pressure Sensor -G65- and the Refrigerant Circuit
Pressure Sensor -G805- only transmits the measured value for the
refrigerant circuit pressure to the connected control module.
The A/C Pressure/Temperature Sensor -G395- transmits the
measured value for the refrigerant circuit pressure and the
measured temperature to the connected control module. Even
though only the pressure signal is evaluated on a vehicle, an
A/C Pressure/Temperature Sensor -G395- is not and must not be
installed on a vehicle for which a High Pressure Sensor -G65- or
a Refrigerant Circuit Pressure Sensor -G805- is designed. Refer
to Parts Catalog.
- The downstream control modules (Radiator Fan Control Module,
Engine Control Module, Front A/C Display Control Head -E87- or
Climatronic Control Module -J255-, etc.) use this signal to
calculate the refrigerant circuit pressure and activate the
radiator fans, the motor, and the A/C Clutch -N25- if necessary,
or to change the activation of the A/C Compressor Regulator
Valve -N280-. Use the Vehicle Diagnostic Tester ("OBD" or
"Guided Fault Finding" function). Refer to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit (vehicle-specific repair manual).
READ NEXT:
There are different versions of this sensor with different
functions and with different names. For exact name, allocation
and notes doe the respective function, refer to
→ Heating, Ventilatio
General Information
Caution
When performing work on refrigerant circuit, observe
all generally applicable safety precautions and pressure
container regulations.
The pressures and temperatur
General Information
Indicators on pressure gauge
1 - Temperature scale for refrigerant R134a CF3-CH2F or
CH2F-CF3.
2 - Pressure scale
Note
Pressure is measured in differe
SEE MORE:
Overview - Name Badges and Emblems
1 -
Emblem
Removing and installing. Refer to
→ Chapter "Radiator Grille Name Badges and Emblems, Removing and
Installing".
2 -
quattro Name Badge
Equipped on some models
Removing and installing. Refer to
→ Chapter "Radiato
Description
Applies to: vehicles with traffic jam assist
Fig. 116 Turn signal lever: button for traffic jam assist and
Audi active lane assist
Traffic jam assist supports the driver when driving
in traffic jams or in heavy traffic.
In a speed range under 40 mph (65 km/h), the
system can help to