Audi Q3: A/C Compressor Regulator Valve -N280-, Checking Switch-On Signal
Special tools and workshop equipment
required
- Vehicle Diagnostic Tester
- Connector Test Set -VAG1594D-
- Probe -VAS5051/8-
Test Sequence
- Remove the noise insulation. Refer to
→ Body Exterior; Rep. Gr.66; Noise Insulation; Noise Insulation,
Removing and Installing.
- Disconnect the connector -2-.
- Re-establish the connection between the connector
-2- and the A/C Compressor
Regulator Valve -N280--item 1-
using an adapter cable from the Connector Test Set -VAG1594 D-.
Note
- The activation of the A/C Compressor Regulator Valve -N280-
and the current measured by the Climatronic Control Module
-J255-/A/C Control Module -J301- control head, which flows via
the A/C Compressor Regulator Valve -N280-, is displayed in the
control head measured values. "Read measured values" using the
Vehicle Diagnostic Tester in the "Guided Fault Finding"
function.
- An adapter cable can also be used for this test. To do this,
for example, use one connector each -A-
and -B- (part number 1J0 973 702
and 1J0 973 802 and related terminal contacts; refer to the
Parts Catalog), two commercially available sockets for banana
connectors -C- and two wires with
0.5 mm 2 diameter.
- Connect the Probe - VAS5051/8- to the adapter cables.
- Measuring cable (signal wire) to contact "2" of connector
-2-.
- Measuring cable (shielding, ground) to contact "1" of
connector -2-.
- Set the operating mode "measuring equipment" DSO (digital
storage oscilloscope) on the Vehicle Diagnostic Tester.
- Select the setting 5V/Div = 0.5 ms/Div (5 V DC and 0.5
milliseconds per unit).
- Start the engine.
- Set the temperature preset for the driver- and front
passenger side to "Lo" on the Climatronic Control Module -J255-
control head. By pressing the buttons Auto
and AC or A/C,
the activation of the A/C Compressor Regulator Valve -N280- is
switched on and off.
- Set the temperature knob to the "cold" stop on the A/C
Control Module -J301- control head. By pressing the button
AC or A/C,
the activation of the A/C Compressor Regulator Valve -N280- is
switched on and off.
The following is displayed on the oscilloscope screen
depending on the control head setting:
- There is no square-wave signal when "OFF" mode is selected
(indicator lamp in the AC or
A/C button does not illuminate) (the
A/C Compressor Regulator Valve -N280- is not activated).
- During "Auto" mode (only automatic climate control system)
and the AC or A/C
button pressed (indicator lamp in the AC
or A/C button illuminates), there is
a square-wave signal with an impulse width
-A- between 75 % and 100 % (the A/C Compressor Regulator
Valve -N280- is activated).
Note
- The illustration shows a signal with a duty cycle of
approximately 80 %.
- The impulse width -A- depends
on the desired cooling output, the electrical system voltage,
etc. (over the width of region -A-,
the current is regulated via the A/C Compressor Regulator Valve
-N280- by the Climatronic Control Module -J255-/A/C Control
Module -J301- control head).
- The signal distance -B- is
always 2 milliseconds. This corresponds to frequency of 500
Hertz.
- The duty cycle is determined by the ratio of impulse width
-A- and signal distance
-B-.
- The impulse width of the square-wave signal changes
depending on the Climatronic Control Module -J255-/A/C Control
Module -J301- control head setting and the measured ambient
influences (duty cycle between 100% and larger than 30%, the A/C
Compressor Regulator Valve -N280- is activated so that the
necessary compressor output to reach the specified temperatures
is achieved).
Note
- With the setting, for example, "Auto" mode (automatic
climate control system), temperature setting "Lo" and the
AC button pressed (indicator lamp in
the AC button illuminates), the A/C
Compressor Regulator Valve -N280- is activated so that the
maximum permissible current of approximately 0.65 A flows via
the A/C Compressor Regulator Valve -N280- (maximum compressor
output).
- In control mode, actuation time is governed by required
cooling output and vehicle electrical system voltage, for
example. It is however always of sufficient duration to achieve
a mean current of 0.3 A.
- Certain functions on the A/C Compressor Regulator Valve
-N280- (for example, a stuck valve or a disruption in the coil)
can lead to a complaint regarding the A/C compressor (A/C system
doesn't cool, the evaporator ices over, etc.). If the cause is
with the A/C Compressor Regulator Valve -N280- (and not the A/C
compressor itself), the A/C compressor can be serviced by
replacing the A/C Compressor Regulator Valve -N280-. Refer to
→ Refrigerant R134a Servicing; Rep. Gr.87; Refrigerant Circuit
Components, Replacing (Refrigerant R134a, Servicing;
Refrigerant Circuit Components, Replacing).
- The A/C Compressor Regulator Valve -N280- is not available
as a replacement part for all A/C compressors. If the A/C
Compressor Regulator Valve -N280- is not available as an
individual A/C compressor part (different versions), then the
entire A/C compressor must be replaced. Refer to the Parts
Catalog.
High Pressure Sensor -G65-, Checking Pressure Signal
Note
- The cooling output cannot be checked when the High Pressure
Sensor -G65- is removed. The Climatronic Control Module
-J255-/A/C Control Module -J301- control head does not switch on
the Air Conditioning (A/C) compressor. "Read measured values"
using the Vehicle Diagnostic Tester in the "Guided Fault
Finding" function.
- After switching off the A/C compressor in this vehicle, it
may take a relatively long time for the pressure on the high
pressure side to decrease. This is because the expansion valve
is cold and the pressure on the low pressure side increases
quickly after shutting the compressor off, then the expansion
valve closes and the refrigerant flows slowly to the low
pressure side.
Test Sequence
- Disconnect the connector -A-.
Routing of 3-pin connector on High Pressure Sensor -G65-
1 - Ground
2 - Signal output - square-wave signal to the Climatronic
Climatronic Control Module -J255-/A/C Control Module -J301- A/C
control head
3 - Terminal "75" (positive)
Note
- With the connector disconnected, the A/C compressor is not
switched on.
- The High Pressure Sensor -G65--B-
is an electronic control module, which creates a square wave
signal, whose duty cycle ratio changes with the pressure in the
refrigerant circuit.
The pressure signal from the High Pressure Sensor -G65-
A - Pressure on the high pressure side of the refrigerant
circuit in bar (absolute pressure)
B - Square-wave signal duty cycle
C - Characteristic curve for the square-wave signal duty cycle
Note
- The Climatronic Control Module -J255-/A/C Control Module
-J301- control head switches the A/C compressor on as soon as
there is no A/C compressor shut-off condition (by activating the
A/C Compressor Regulator Valve -N280-). Refer to Vehicle
Diagnostic Tester in the "Guided Fault Finding" function.
- The A/C control head switches the A/C compressor on at a
duty cycle larger than approximately 12% (corresponds to
approximately 1.2 bar (17.4) absolute pressure) and less than
approximately 78% (corresponds to approximately 32 bar (464 psi)
absolute pressure), if no other shut-off condition is in effect.
- If the duty cycle is greater than 12% (corresponding to
approximately 1.2 bar (17.4) absolute pressure) and less than
78% (corresponding to approximately 32 bar (464 psi) absolute
pressure).
- The A/C compressor is not switched on if the duty cycle is
smaller than 12% or greater than 78% (the A/C Compressor
Regulator Valve -N280- is not activated).
- The duty cycle and the pressure calculated by the
Climatronic Control Module -J255-/A/C Control Module -J301- are
displayed as a measured value. Refer to Vehicle Diagnostic
Tester in the "Guided Fault Finding" function.
- In terms of absolute pressure, 0 bar corresponds to an
absolute vacuum. Normal ambient pressure equals approximately
1.0 bar (14.5 psi) absolute pressure. 0 bar pressure corresponds
to an absolute pressure of approximately 1.0 bar (14.5 psi) on
most pressure gauge scales (indicated by "-1" below "0").
- Depending on the calculated refrigerant circuit pressure
with the A/C compressor activated, the Climatronic Control
Module -J255-/A/C Control Module -J301- control head sends a
request for an increased Coolant Fan -V7- speed to the engine
control module via the data bus. It activates the Coolant Fan
-V7- directly or via the Coolant Fan Control Module -J293-
(depending on the version with a certain refrigerant circuit
pressure, or depending on the pressure as soon as the A/C
compressor is switched on). The request determined by the Climatronic Control Module -J255-/A/C Control Module -J301-
control head is displayed as a measured value. Refer to Vehicle
Diagnostic Tester in the "Guided Fault Finding" function.
- The request to activate the Coolant Fan -V7- is currently
only sent to the data bus system at a certain refrigerant
circuit pressure by the Climatronic Control Module -J255-/A/C
Control Module -J301- A/C control head. If the pressure in the
refrigerant circuit is greater than approximately 9 bar (130
psi) (6 bar (87 psi), if the pressure was previously greater
than 9 bar) and less than 20 bar (290 psi), a request from 30 to
100% takes place, depending on pressure.
- If the refrigerant circuit pressure is less than
approximately 9 bar (130 psi) (6 bar (87 psi), if the pressure
was greater than 9 bar (130 psi) before), there is currently no
request to activate the Coolant Fan -V7- by the Climatronic
Control Module -J255-/A/C Control Module -J301- A/C control
head.
- If the refrigerant circuit pressure is greater than
approximately 20 bar, a request is currently sent to activate
the Coolant Fan -V7- at 100% by the Climatronic Control Module
-J255-/A/C Control Module -J301- A/C control head (depending on
the version of the engine control module/Coolant Fan Control
Module -J293-, the actual activation may be less than 100%).
- The signal generated from High Pressure Sensor -G65- is also
used to control the engine. The Climatronic Control Module
-J255-/ A/C Control Module -J301- control head sends the
information to the engine control module via the data bus system
(the necessary torque to drive the A/C compressor depends on the
refrigerant circuit pressure). Depending on the engine control
module version, the signal under "Read measured values" is
displayed as a duty cycle (for the respective installed engine
control module). Refer to Vehicle Diagnostic Tester.
This image appears on oscilloscope screen (for example, on
the Vehicle Diagnostic Tester) when the following conditions are
met.
- Ignition switched on (positive at contact "3" and ground at
contact "1" on High Pressure Sensor -G65- present)
- Oscilloscope setting: 5 V/div. DC (5 V per unit DC) 5
ms/div. (5 milliseconds per unit)
- Measuring cable (signal wire) connected to contact "2" on
High Pressure Sensor -G65-.
- Measuring cable (shielding) connected to contact "1" (ground
on High Pressure Sensor -G65-).
Note
- The illustration shows the signal, which is sent when the
refrigerant circuit pressure is approximately 7 bar (101.52 psi).
This conforms to a approximate 25% duty cycle. With compressor
not engaged, an ambient temperature of 30 ºC (86 ºF) and
properly filled refrigerant circuit.
- The impulse width -A- depends
on the pressure in the refrigerant circuit (if pressure
increases, area -A- gets wider).
- The signal distance -B- is
always 20 milliseconds. This corresponds to frequency of 50
Hertz.
- The duty cycle is determined by the ratio of impulse width
-A- and signal distance
-B-.
- For example, use the measuring cables from the Connector
Test Set -VAG1594D- or an adapter cable for this test. To do
this, for example, use one connector each
-A- and -B- (part number
-1J0 973 703- and -1J0 973 803- and related connector terminals;
refer to the Parts Catalog), two standard sockets for banana
connectors -C- and three wires with
0.5 mm 2 diameter.
READ NEXT:
Handling Refrigerant Safety Precautions
The assemblies and piping system of the air conditioner are
filled with the following refrigerant:
1.1.1.2 Tetrafluorethane (CF3-CH2F
or CH2F-CF3)
Curren
Even slight contamination can lead to defects. Therefore
observe the following rules for cleanliness when working on the
A/C system:
Immediately seal the open lines and connections with clean
SEE MORE:
Setup
Applies to: vehicles with smartphone interface
You can connect your smartphone to the MMI
with a cable or wirelessly using the smartphone
interface. Certain content on your smartphone is
adapted in the MMI while driving and can be operated
through the MMI.
Connecting smartphones with a cable
R
1 - Center Console
Overview. Refer to
→ Chapter "Overview - Center Console".
2 - Driver Side Instrument Panel Cover
Overview. Refer to
→ Chapter "Overview - Driver Side Instrument Panel Cover".
3 - Trim Panel
For the steering column