Audi A6 Air Conditioning Repair by Roade Main Garage: Hidden Fault 00256, Lasting Fix
When Mr C brought his Audi A6 to Roade Main Garage in Northampton for its regular service, he mentioned that the air conditioning had stopped cooling properly. Assuming it might just need a re-gas, he asked our technicians to check it while the car was with us.
During the service, we confirmed that the refrigerant level was correct and the system was completely sealed. Yet, despite everything appearing normal, the air conditioning still refused to produce cold air. That told us the issue was not a simple maintenance problem but something deeper within the system.
We advised Mr C that a separate diagnostic appointment would be needed to investigate further. When the vehicle returned, our team began a methodical testing process using genuine Audi wiring data and diagnostic tools to identify exactly what was stopping the system from working.
Read on to find out how our specialists at Roade Main Garage in Northampton traced a hidden electrical fault and restored the Air Con system to full performance.
Audi A6 Air Conditioning Repair: Beginning the Search for the Fault
After completing the service, Mr C returned to Roade Main Garage in Northampton so our technicians could take a closer look at the Audi A6 AC not working. During the earlier inspection, we had confirmed that the refrigerant level was correct and the system was fully sealed. Despite that, the air conditioning still refused to produce any cold air.
With no leaks or refrigerant issues present, it was clear that something more technical was preventing the system from working. Our first step in getting to the bottom of it was to perform a complete system scan to check for any electronic communication faults. The results provided our first important lead:
00256 – Air Conditioning Pressure/Temperature Sensor (G395): No Signal/Communication
This component, known as the G395 pressure temperature sensor, constantly measures both the pressure and temperature of the refrigerant and sends that data to the control module. If the system cannot receive that signal, it won’t activate the compressor — a built-in safety feature to protect the air conditioning circuit.
At this point, it was too early to say whether the issue was caused by a faulty sensor or a wiring fault affecting its communication. The next s
What Our Diagnostic Tests Finally Revealed
With the earlier tests complete, our next step was to locate where the system had lost communication with its G395 pressure temperature sensor.
Using the Right Data and Tools
To guide the next stage of diagnosis, we referred to Audi’s official wiring diagrams and technical data. These resources detail how the G395 pressure temperature sensor receives power, shares an earth, and communicates through the LIN network that connects to the air conditioning control module.
Using this information, our technician connected an oscilloscope to the sensor connector and began checking each wire for activity:
- Power supply: Correct voltage was present and stable.
- Earth: Ground integrity was confirmed.
- Signal line: No communication signal detected.
The results showed that, although the sensor had power and earth, no data was being transmitted back to the control module. That suggested an interruption in the communication pathway somewhere between the sensor and the main network.
Comparing Signals Across the System
To confirm this, we compared the readings with another sensor that operated on the same LIN circuit. The second signal appeared normal, with a clear digital pattern showing the network was communicating correctly elsewhere.
This ruled out a wider system fault and narrowed the problem down to the wiring between the G395 pressure temperature sensor and the next junction point in the communication circuit.
Tracing the Break
Following the wiring down its full length, our technician tested continuity and voltage at each connector from the control module towards the front of the vehicle. The signal remained strong until we reached a connector hidden behind the passenger-side trim, which indicated the break was further forward in the loom.
That section of wiring runs across the nearside front wheel arch and beneath the headlamp. When we opened the protective conduit, the real fault was revealed: a section of corroded wiring hidden inside the loom. Moisture had entered the insulation, degrading the copper strands and cutting the LIN communication line.
This corrosion had prevented the G395 pressure temperature sensor from sending the vital pressure and temperature data the system needs to activate.
With the fault now located and confirmed, our next task was to repair the damaged wiring and restore communication across the network.
How the Wiring Was Repaired and the System Restored
With the cause of the fault identified, the next step for our Northampton Audi specialists was to repair the damaged wiring and restore communication between the G395 pressure temperature sensor and the air conditioning control module. Before beginning the work, we explained our findings to Mr C and outlined the repair process. Once he was happy to proceed, the repair began.
Accessing the Fault Area
The damaged section of wiring was located within the harness that runs over the nearside front wheel arch and beneath the headlamp. During the diagnostic process, we had already removed the protective sleeve to reveal the affected wire, giving our technician full access to carry out the repair safely and accurately.
Preparing and Repairing the Wiring
Working in line with Audi’s wiring repair standards, our technician completed the work carefully and methodically:
- Removed the corroded wire section on both sides of the damage to expose clean, bright copper.
- Installed a new piece of matching-gauge automotive wire to restore full continuity.
- Secured all joins with correctly crimped and sealed connectors to prevent future corrosion.
- Checked continuity across the circuit to confirm a stable and reliable repair.
Testing the Repair
After the wiring had been repaired, we reconnected the oscilloscope to confirm that the LIN communication signal had been restored. This time, the signal appeared strong and consistent, showing that data was once again reaching the control module.
The G395 pressure temperature sensor was then reconnected, the fault code cleared, and the system restarted. The compressor came online immediately, and the air conditioning began delivering cold air through the vents. A final system scan showed no remaining errors.
With the repair completed and the connection re-established, Mr C’s Audi A6 air conditioning system was back to full working order. It was performing exactly as intended and ready to keep Mr C cool for miles to come.
A Thorough Repair and a Great Outcome
For Mr C, the difference was clear as soon as the repair was complete. His Audi A6’s air conditioning was once again producing cold air, restoring both comfort and confidence in the system. What he first suspected to be a simple re-gas issue turned out to be a much more complex fault, but thanks to our skilled technicians at Roade Main Garage, the system was brought back to full health.
Each stage of the work — from diagnosing the fault to confirming the repair — was completed using Audi’s official wiring data and professional repair procedures. This ensured the repair met the same high standards expected by the manufacturer.
For our team, this successful Audi A6 air conditioning repair was about more than fixing the symptom; it was about finding the true cause, resolving it correctly, and returning the car in perfect working order.
Roade Main Garage – Reliable Audi A6 Air Conditioning Repairs You Can Count On
At Roade Main Garage in Northampton, we take pride in offering professional repairs backed by honest communication and genuine care for our customers. This recent Audi A6 air conditioning repair showed how our structured diagnostic approach and attention to detail can turn a complex electrical fault into a lasting, reliable fix.
Every repair we complete is carried out using manufacturer data, approved wiring methods, and careful testing to ensure long-term reliability. Whether it’s an electrical fault, communication issue, or a sensor failure, our technicians have the knowledge and experience to put it right.
Here’s what you can expect when you choose Roade Main Garage:
- Skilled technicians trained in modern Audi systems
- Straightforward communication and clear repair advice
- Genuine technical data and professional repair procedures
- Competitive rates compared with main dealers
- 12-month parts and labour guarantee
Courtesy car options are available to keep you on the move while your vehicle is with us.
We proudly serve drivers across Northampton and Milton Keynes, with a {{average-rating}} star Google rating from {{review-count}} satisfied customers who trust us for expert, dependable service.
If your Audi A6’s air conditioning has stopped performing as it should, call Roade Main Garage on 01604 862262. Our technicians will diagnose the issue accurately, repair it correctly, and get your system back to full performance.
