SQ5 HVAC Temperature Sensor Causing Multiple Failures

Had a similar temperature sensor malfunction on my 2019 S4. The cooling system started acting up and the HVAC system completely shut down. The scan revealed issues with the heat exchanger temperature sensor, which was causing the control unit to receive incorrect readings. The repair required replacing both the faulty sensor and the AC control module. This was a serious issue that needed immediate attention since driving without proper temperature regulation can lead to more extensive damage to the vehicle maintenance systems. The root cause was a corroded wiring harness connected to the temperature sensor, which created communication errors between components. The repair involved: Complete diagnostic of the HVAC system, Replacement of the temperature sensor assembly, Installation of new wiring harness, Reprogramming of the climate control module The entire job took about 6 hours at the shop. This is not a DIY repair as it requires specialized diagnostic equipment and programming capabilities. Its important to have this fixed by a qualified technician who can properly calibrate the new components after installation. Since the repair, the system has worked flawlessly with no error codes or malfunctions. Regular vehicle maintenance checks can help catch these issues before they lead to complete system failure.

Thanks for sharing your experience with the S4 sensor issue. Sounds very similar to what Im dealing with on my SQ5. Did you remember roughly how much the total repair cost came to? Also curious if youve had any other engine cooling or HVAC system problems since getting it fixed? The temperature gauge on mine is now acting up too so wondering if I should expect more issues. Just want to be prepared before heading to the shop since these repairs can get expensive. The dealership estimate seems really high compared to independent shops.

After getting the temperature sensor heat exchanger replaced, my SQ5s engine cooling system has been working perfectly. The sensor calibration was spot on and I havent experienced any additional HVAC or cooling system problems in the last 6 months. The total repair bill came to 980 Euro for fixing the air conditioning control unit. This included the parts, labor, and complete system testing. While this might seem steep, having a certified technician handle the repair was worth it since they properly diagnosed and fixed all the connected issues. The temperature gauge problems you mentioned could be related to the same sensor malfunction. Its best to have this checked soon since faulty readings can impact the entire cooling system performance. The repair costs at dealerships are typically higher, but they often have better diagnostic tools and direct access to manufacturer parts. Just make sure wherever you go, they perform a full system diagnostic before starting repairs. This helps prevent replacing parts unnecessarily and ensures all related components are working correctly after the fix.

Thanks for the feedback. I finally got my SQ5 fixed last week and wanted to share my experience. Took it to an independent shop that specializes in German cars. They found multiple issues with the cooling system, including a faulty temperature sensor and some coolant leaks around the heat exchanger. The total repair came to 1250 Euro, which included: New temperature sensor, Heat exchanger replacement, Fresh coolant, System pressure testing, AC recharge The shop took about 2 days to complete everything but did a thorough job. They showed me the old parts and explained what had failed. The temperature gauge is now working correctly and the AC blows ice cold again. No more error codes on the dashboard either. Definitely worth paying a bit more to get it done right rather than trying cheaper fixes that might not last. Will be keeping a closer eye on the cooling system maintenance going forward to catch any issues early.