Cold Start Issues & High Fuel Use in Audi A5 TDI

Had the same electrical fault on my Audi A4 2.0 TDI (2012) last winter. The heat not working properly during cold starts was the first sign, followed by increased fuel consumption. The diagnostic confirmed a defective PTC auxiliary heating element. The heating system relies heavily on this component, especially in diesel engines during cold weather. When it fails, the engine needs to work harder to reach optimal temperature, causing rough running and higher fuel usage. The repair involved replacing the complete heating element assembly since individual parts are not serviceable. This is a serious issue that needs addressing promptly as it can lead to additional strain on other engine components and continued poor fuel economy. The job took about 4 hours at the workshop. The heater repair required removing several components to access the heating element location. If you notice these symptoms, best to have it fixed before it affects other systems or leaves you without proper cabin heating in cold weather. Looking at your mileage and symptoms, they match exactly what I experienced. Would recommend having it checked by a shop that specializes in Audi heater systems.

Thanks for sharing your experience with the heating element issue. This matches my situation perfectly. The rough running and high fuel consumption really hit my wallet hard until I got it fixed. Just wondering, do you remember roughly how much the entire heater repair ended up costing? Also, has your temperature control system been working properly since the fix, or have you noticed any other issues popping up? Asking because Im trying to budget for this repair and want to make sure I fix it right the first time, especially before the weather gets any colder and the blower motor has to work overtime.

After visiting my Audi specialist, I can confirm the heating system repair was worth every cent. The total cost came to 350 Euro for replacing the defective electric auxiliary heater, including labor. Since the repair, the HVAC system has been working flawlessly. No more cold air issues during startup, and fuel consumption returned to normal levels. The heating element replacement solved all the problems, rough running, excessive fuel use, and poor temperature control. The mechanic showed me the old heating element, and it was clearly worn out. Getting it fixed before winter was definitely the right call, as a failing PTC heater can really strain other components in cold weather. For anyone else facing similar symptoms: rough cold starts and high fuel consumption in diesel engines often point to auxiliary heater problems, and postponing the repair usually leads to bigger issues down the line.

Thanks everyone for the helpful replies. I took my A5 to a specialist workshop last week and got everything sorted. The total repair came to 380 Euro, slightly more than expected but worth every cent. The mechanic confirmed the PTC heating element was shot and showed me the damaged part. He mentioned catching it early prevented additional strain on the blower motor and other HVAC system components. Been driving for about a week now and the difference is night and day. The cold starts are smooth, fuel consumption is back to normal, and the heating system works perfectly. No more check engine light either. Really glad I asked here first instead of going with the first shop that quoted nearly double this price. Having proper heat again makes winter driving much more bearable.