Golf TDI HVAC & Sensor Issues Need Expert Diagnosis

Had similar symptoms on a Passat 2.0 TDI last summer. The HVAC system shutdown was indeed connected to the heat exchanger sensor malfunction. The temperature gauge readings were unstable, causing the control unit to enter fail-safe mode. Initial diagnosis pointed to sensor calibration, but thorough testing revealed a more complex issue within the cooling system. The heat exchanger had accumulated debris, restricting proper coolant flow and causing erratic temperature readings. Vehicle maintenance records showed the cooling system hadnt been serviced for several years. The repair required: Cooling system flush, Heat exchanger cleaning, New temperature sensor installation, Control unit recalibration It was a serious repair taking 2 full days at the workshop. The car runs perfectly now with stable temperature readings and fully functional HVAC system. Based on your description, the symptoms match closely. Would recommend getting a second opinion from another certified workshop, as sensor calibration alone might not address the root cause. Important: neglecting these symptoms risks more severe engine cooling issues. Best to address it promptly despite past negative experiences with mechanics.

Thanks for sharing your experience. This definitely helps as the symptoms match what Im seeing. The sensor issues and HVAC problems sound identical to my situation. The suggestion about checking the entire cooling system instead of just the sensor makes a lot of sense, especially given the age of my car. Can you remember roughly how much you paid for the complete repair? Also curious if youve had any recurring sensor malfunction or cooling issues since the fix?

After getting the repairs done, I can confirm it was the right decision to fix both the temperature sensor heat exchanger and the air conditioning control unit. The total came to 980€ for the complete job, which included replacing the defective components and recalibrating the system. Since the repair, the temperature gauge has been working perfectly stable and the HVAC system functions as it should. No sensor malfunction or cooling system alerts have appeared on the dashboard in the months following the fix. The engine cooling now maintains consistent readings, unlike before when the values would fluctuate unpredictably. The original diagnosis of a faulty temperature sensor proved accurate, and addressing both issues together was more cost-effective than handling them separately. The cooling system now works flawlessly in all weather conditions. This comprehensive repair approach prevented what could have developed into more serious engine problems if left unaddressed.

I took my car to a certified workshop last week after reading the responses here. The mechanic confirmed it was more than just a sensor issue. They found a minor coolant leak near the heat exchanger that was affecting the temperature readings. The full repair included: New temperature sensor, Heat exchanger repair, Complete system flush, Sensor calibration, HVAC control unit check Total cost was 890€ and took about a day and half. The dashboard error is now gone and the HVAC works perfectly. The temperature readings are stable and the engine runs much smoother. Definitely glad I had the whole cooling system checked rather than just replacing the sensor. The vehicle maintenance history helped identify that the cooling system hadnt been serviced in the past 3 years, which contributed to the problem. Regular coolant changes could have prevented this issue. Will make sure to keep up with the maintenance schedule from now on.