A/C - System Is Inoperative/Blower Motor Functions
87 Air conditioning inoperative
87 12 32
2020124/7
September 5, 2012.
Supersedes Technical DIAGNOSIS AND REPAIR Group 87 number 12 - 29 dated July 23, 2012 for reasons listed below.
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Affected Vehicles
Condition
^ Air conditioning is inoperative.
^ The HVAC blower functions normally.
^ Battery discharged; however, when charged, there is no bus silence when vehicle ignition is off.
Technical Background
^ The A/C Pressure/Temperature Sensor G395 leaks refrigerant. This causes Sensor G395 to show an incorrect or implausible value when reading
MVBs. An incorrect signal or a low refrigerant level in the system can cause the air conditioning compressor to deactivate.
^ The LIN cable connecting the J519 Central Electrics Control unit to Sensor G395 is pinched or cut. This affects the A4/S4, A5/S5 Coupe and
Cabriolet, and Audi Q5 vehicles. The A6 and A8 are not affected by this type of failure.
^ The pressure sensor G395/G65 sends an incorrect signal that prevents bus silence and the battery is discharged.
Tip: Sensor G395 is a LIN slave of Vehicle Electrical System Control Module J519. Vehicle Electrical System Control Module J519 transfers the
information provided by the sensor via the comfort data bus to Climate Control Module J255.
Production Solution
An improved A/C Pressure/Temperature Sensor G395 was introduced into series production and the wiring manufacturers processes were optimized.
Service
For A4/S4 (8K), A5/S5 Coupe/Cabriolet (8T/8F), Audi Q5, A6, A8:
If DTCs are stored in the J255 Climate Control Module for the G395 pressure sensor, then check the system pressures and refrigerant volume.
^ If system pressures and refrigerant volume are low, check for refrigerant leaks at G395. If a leak is found, then replace the G395.
^ If the system pressure and refrigerant volume are correct, perform guided fault finding. If an implausible pressure value is found in MVB
1, field 4, then replace G395.
Tip: Install only the improved G395. See part numbers in Required Parts and Tools.
Only for A4/S4 (8K), A5/S5 Coupe/Cabriolet (8T/8F), Audi Q5:
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1. Check for these four DTC codes:
DTC 00457 (Vehicle Electrical System Control Module - J519- Please check DTC memory) in Climate Control Module J255, address 08.
DTC 00256 (A/C Pressure/temperature Sensor -G395- Incorrect Signal) in Climate Control Module J255, address 08.
DTC 01592 (Air Quality Sensor -G238- No signal/communication)
DTC 00256 (A/C Pressure/temperature Sensor -G395- No signal/communication) in Vehicle Electrical System Control Module J519, address
09.
If DTCs a, b, d are stored only perform steps 2-6.
If all DTCs (a, b, c, d) are stored, only perform step 7.
Tip: The existing LIN cable connecting the J519 Vehicle Electrical System Control module to the G395 Pressure Sensor could be pinched or
cut if DTCs a, b, d are stored.
2. Check the LIN cable connecting the J519 Central Electrics Control unit to the G395 pressure sensor according to guided fault finding.
3. Check the wire terminals in the connector at the G395 pressure sensor for proper attachment, possible corrosion, and for any pins that may be
pushed back or widened.
4. Check to make sure there is proper voltage going to the sensor and verify the ground is not intermittently open (wiggle test).
5. Check the integrity of the wire harness.
There are two known sections in the wiring harness that can be affected, but the potentially affected areas are not limited to these two known
sections. One of the known sections is in the drivers footwell area where the wire harness enters the interior of the car from the engine bay
(Figure 1).
The second known section is in the wire harness located under the drivers side headlight (Figure 2).
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6. If a cut wire is found, install an overlay wire for the LIN bus signal. Do not attempt to repair the existing wire harness.
a. Route the new LIN bus wire from the power system control unit J519 to the sender for refrigerant pressure/temperature G395 so that it
enters the interior of the vehicle through the drivers side fender/lower A-pillar area through the grommet indicated in Figures 3 and 5.
Tip: Do not route the wire through the same opening used by the existing wire harness.
Tip: The LIN bus between J519 and G395 may contain a junction point shared with other modules depending on the vehicle. Ensure to
maintain the junction points when routing the overlay.
On vehicles with a charisma switch (ride selection switch located on the instrument panel) route the new cable of the sender for refrigerant
pressure/temperature G395 to junction B549 as indicated by the red arrow in Figure 4.
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b. Seal off the opening around the wire with Butyl sealant to prevent water intrusion.
7. Replace the sender for refrigerant pressure/temperature G395.
Warranty
Required Parts and Tools
Additional Information
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service
manuals for the latest information.
