VW Touran AC & Sensor Failure, Mechanic Help Needed

Recently dealt with similar symptoms in my 2011 VW Golf 1.4 TSI. The temperature sensor failure in the heat exchanger caused cascading issues throughout the HVAC system. Initially noticed the AC stopped working and the temperature gauge readings became erratic. The repair involved replacing both the faulty sensor and part of the control unit. The original diagnosis pointed to just the sensor, but further testing revealed the control unit had also been damaged due to incorrect temperature readings. This is a known weak point in these TSI engines. The coolant leak check showed the heat exchanger itself was intact, which was fortunate as that would have been a much more extensive repair. The cooling system needed a complete flush to remove contamination that had built up around the failed sensor. This repair required specialized diagnostic equipment to properly calibrate the new sensor with the HVAC system. Its not a DIY-friendly fix since accessing the components means partially dismantling the front of the engine bay. The entire repair took about 6 hours of labor. The good news is that once properly fixed, these systems typically remain reliable. But getting an accurate diagnosis is crucial, having the right diagnostic tools and experience with VW cooling systems makes a big difference in the repair outcome.

Thanks for the detailed response about your Golf repair. My Touran seems to be showing identical symptoms with the temperature sensor and HVAC problems. After reading about your experience, I feel more confident about what needs to be done. Quick follow up, do you remember roughly how much you paid for the complete repair? Also, has everything been working properly since the fix? Im particularly concerned about the temperature gauge readings staying consistent after repair.

Since having the temperature sensor heat exchanger replaced at a VW specialist, my car has been running perfectly. The temperature gauge now shows consistent readings and the AC works flawlessly. The repair costs came to 980€ total, which included the new control unit, sensor replacement, and the complete system calibration with their diagnostic equipment. The cooling system also got a thorough flush as part of the service, which helped ensure everything works as intended. Its been about 8 months now, and I havent experienced any temperature-related issues or AC problems since the fix. The sensor calibration was done properly, which is crucial for long-term reliability. The investment was worth it considering how critical these components are for proper engine operation. When the temperature sensor fails, it can cause wider system damage if left unaddressed, so getting it fixed properly the first time is important.

I finally got the Touran fixed last week and wanted to share my experience. Found a specialized VW workshop through a local owners forum. The mechanic confirmed the same issues you mentioned, faulty temperature sensor in the heat exchanger affecting the entire HVAC system. Total repair cost was 890€, which covered replacing the sensor, flushing the cooling system, and recalibrating everything with their diagnostic equipment. They also found a small coolant leak near the sensor connection which they fixed as part of the service. The whole job took about 5 hours. The temperature gauge now shows steady readings and the AC is working perfectly again. The shop provided a detailed breakdown of what they replaced and why, which was refreshing compared to my previous mechanic experiences. Really glad I didnt try fixing this myself, the diagnostic equipment they used to calibrate the new sensor would have been impossible to access otherwise. The thorough cooling system flush also revealed some debris that could have caused sensor malfunction again if left unchecked.