Audi A6 Cold Start Roughness + High Fuel Consumption

Had a similar issue with my 2014 Audi A4 2.0 TFSI. The cold start problems turned out to be related to a faulty electrical fault in the PTC auxiliary heating system. The heating element was defective, causing increased fuel consumption as the engine tried to compensate for the lack of proper heating. The HVAC system kept struggling to produce sufficient cold air in summer and warm air in winter. After diagnostic testing, the issue was traced to the auxiliary heater control module, which needed replacement along with the heating element assembly. This was a serious repair requiring specialized diagnostic equipment to properly identify the fault codes. The entire heating system needed inspection since these components are interconnected. When the auxiliary heater fails, it puts additional strain on the engine during cold starts, leading to rough running and increased fuel usage. Worth checking the auxiliary heater fuse and relay first, but given the symptoms and engine light, its likely a component failure. This repair requires removing parts of the dashboard to access the heating system components. Best handled by a shop familiar with Audi electrical systems.

Thanks for sharing your experience. It sounds exactly like what Im dealing with, rough cold starts and the heat not working properly. My blower motor also makes a strange noise now. Did you get it fixed at the dealer or independent shop? Would help to know the repair costs to budget for this. Has everything been working fine since the heating system repair?

Since getting the PTC heater issue fixed last month, my Audi temperature control system has been working flawlessly. No more cold start issues or strange noises from the blower motor. The HVAC system is now delivering proper heat, and fuel consumption returned to normal. I went with a certified Audi specialist who diagnosed and repaired the electric auxiliary heater defect. The total repair cost was 350 Euro, which included the replacement part and labor. It took them about 4 hours to complete the job since they had to access several components behind the dashboard. The heating element replacement resolved all the symptoms, no more rough starts, proper cabin heat, and the engine check light cleared up. Definitely worth getting it properly diagnosed and repaired rather than trying temporary fixes that could lead to bigger problems.

Took my car to Auto Tech Solutions after reading your advice. Really glad I did, turns out you were spot on about the PTC heater being the culprit. The electrical fault was causing all those cold start problems. The mechanic found the heater control module was completely shot, which explained the blower motor noise and poor temperature control. Total bill came to 380 Euro for parts and labor. About what you mentioned, though they had to keep the car for a full day to properly test the HVAC system after the repair. Been a week now and the difference is night and day. No more rough starts, heat works perfectly, and fuel consumption is back to normal. Engine light is finally off too. Should have dealt with this sooner but wanted to be sure about the cause first. Thanks again for pointing me in the right direction with the heating system diagnosis.