VW Up Temperature Sensor Malfunction Causes AC Failure

I had a very similar issue with my VW Polo 1.0 TSI from 2018. As someone who has some experience working on cars, I first thought it was just a temperature sensor giving false readings. The symptoms matched exactly what you describe, HVAC system errors and engine cooling warnings. After attempting basic troubleshooting of the temperature gauge readings, I took it to my regular workshop. They diagnosed a complete failure of the air conditioning control unit, which was affecting both the AC operation and sending incorrect signals to the engine management system. The repair included: Full diagnostic scan, Replacement of the AC control unit, Recalibration of the temperature sensors, Testing of the heat exchanger system Total cost was 980€ and took about 6 hours to complete. The issue never came back after the fix. To better assist with your specific case, could you share: Complete error codes showing on the dash, Whether the temperature gauge shows normal readings, If the AC was working intermittently before failing completely, Any unusual sounds from the HVAC system These details would help determine if your issue is identical to what I experienced with my Polo.

Last service was at 65000km in February, and after dealing with similar symptoms, I can confirm the sensor malfunction was causing both AC and engine cooling issues. The workshop diagnosed a faulty temperature sensor and heat exchanger unit. They performed a complete sensor calibration which resolved both the HVAC system errors and engine warnings. Total repair cost came to 420€ including labor. The key was correctly diagnosing which temperature gauge was malfunctioning, turns out the primary sensor was sending incorrect readings to both systems. Unlike some cases where the entire control unit needs replacement, this was a more straightforward fix. Would be glad to provide the part numbers used if needed.

I can confirm these findings match perfectly with my VW Polo experience. After further investigation of my case, the root cause was indeed similar, a faulty primary temperature sensor affecting multiple vehicle systems. While my initial repair was more extensive with the full control unit replacement, subsequent cases in the owner forums showed that a focused sensor replacement and calibration often solves the issue. The 420€ repair cost sounds much more reasonable than what I paid. The interaction between the cooling system and HVAC system is quite intricate in these VW models. A single malfunctioning sensor can trigger multiple error codes and affect various systems. The vehicle maintenance history plays a big role, regular checks of the cooling system components could help catch these issues early. For future reference, monitoring the temperature gauge behavior and any irregular HVAC system operation can provide early warning signs. When the sensor starts failing, you might notice subtle inconsistencies before complete system failure occurs. Have you noticed any changes in fuel consumption since the repair? In my case, the proper sensor calibration actually improved efficiency slightly.

Thanks for sharing that detailed follow-up. After the temperature sensor calibration and repair, I did notice an improvement in fuel economy, dropping about 0.4L/100km on average. The vehicle maintenance technician explained this was due to the engine now running at optimal temperature. Both the HVAC system and cooling system have been working flawlessly for the past 3000km. The temperature gauge now shows consistent readings across all driving conditions. No more error messages or warning lights on the dash. My main takeaway from this experience is the importance of proper sensor calibration and how interconnected these systems are. What seemed like a complex multi-system failure was ultimately traced to a single faulty temperature sensor. For anyone searching the forums with similar issues: keep in mind that the repair cost can vary significantly depending on whether you need a full control unit replacement or just sensor replacement and calibration. Getting a proper diagnostic scan is crucial before any repairs.