A8 Cold Start Issues Linked to Faulty PTC Heater

Had nearly identical issues with my 2019 A6 3.0 TDI. The PTC heater failure started with poor heating during cold starts and increased fuel consumption since the engine had to work harder to reach operating temperature. The electrical fault in the heating element turned out to be more serious than initially suspected. The complete auxiliary heater assembly required replacement, along with some wiring harness repairs due to heat damage. This is a known weak point in these diesel engines, especially during winter operation. The symptoms match exactly, poor initial cabin heat, cold air at idle, and the engine taking longer to warm up. The heater repair involved removing several components from the engine bay to access the PTC unit. Without proper heating support, these diesel engines struggle to maintain optimal operating temperatures, leading to increased fuel usage and potential long-term issues if left unaddressed. Would strongly recommend getting this checked soon, as continued operation with a faulty PTC heater can lead to additional complications with the engine management system and emissions control. The complete repair took about 6 hours at the workshop, but the car has been running perfectly since, with normal fuel consumption and proper heat output restored.

Thanks for sharing your experience with the PTC heater replacement. My A8 ended up getting fixed last month with similar symptoms. The blower motor also needed replacement since it was damaged from the faulty heating element. The HVAC system works perfectly now, but I am curious about the repair costs. Do you remember how much you paid for the complete job? Also, have you noticed any other issues coming up since the repair?

After seeing the mechanic, the PTC heater problem was completely resolved. The total repair cost came to 350 Euro for fixing the defective electric auxiliary heater. This was actually less expensive than I initially feared given the complexity of accessing the HVAC system components. The cold air issues disappeared immediately after the repair, and fuel consumption returned to normal levels since the engine no longer struggles to maintain proper operating temperature. The heating element replacement has held up perfectly with no additional problems over the past months. The repair was definitely worth the investment, especially considering how the faulty PTC heater could have led to more serious engine management issues if left unfixed. The HVAC system now warms up quickly during cold starts, and the cabin heat distribution works exactly as it should. No other related issues have emerged since the heater repair was completed. If anything, the car runs more efficiently now that the heating system is functioning correctly.

Thanks everyone for the helpful replies. I finally got my A8 fixed last week and wanted to share the outcome. After taking it to a different mechanic who specializes in temperature control systems, they diagnosed both a faulty PTC heater and worn blower motor. The total repair came to 890 Euro, which included the heating system components and labor. While higher than expected, the thorough job made a huge difference. The cold starts are smooth now, cabin heats up quickly, and fuel economy is back to normal. The new mechanic also found some minor wiring issues that the previous shop missed. The whole repair took just under a day, but the results were worth the wait. Three weeks later and everything is still working perfectly, no more cold air problems or error codes. Just wanted to close the loop on this thread since the advice here helped point me in the right direction for getting it properly diagnosed and fixed.