Audi A4 Cold Start Struggles: Heating System Suspect

After seeing similar symptoms on my 2004 Audi A6 2.0T, the heating system issue turned out to be significant. The PTC (Positive Temperature Coefficient) auxiliary heater was completely defective, causing poor cold starts and increased fuel consumption. The heater repair involved replacing both the heating element and related electrical components. The blower motor was working fine, but the auxiliary heating system wasnt providing the needed warmth during cold starts, making the engine compensate by running rich. This explained the higher fuel usage and rough running. The check engine light came on because the system detected the heating element failure. The repair required specialized diagnostic equipment to properly identify all affected components. Its not a simple fix, the entire heating element assembly needed replacement along with some wiring harness components. Without proper repair, these symptoms typically worsen and can lead to starting reliability issues. Given your symptoms match exactly what happened with my A6, suggest having a certified shop that specializes in Audi heating systems handle this repair. When heat not working properly during cold starts, it usually indicates the PTC heater assembly has failed, rather than being a minor issue.

Thanks for sharing that experience with the A6. Im dealing with the exact same cold start and heating system problems right now with my A4. Just took it in last week and got similar diagnostic results about the PTC heater. Would you mind sharing how much the repair ended up costing you? Also curious if youve had any other temperature control or HVAC system issues since getting it fixed. Want to make sure I budget correctly and know what to watch out for going forward.

Good news on the electrical fault that was causing the cold start problems, got it fixed last week. The mechanic found the PTC auxiliary heater was indeed completely dead, just as suspected. The total repair came to 350 Euro, which included replacing the heater element and some related wiring. Since the heating system repair, cold starts have been perfect and fuel consumption is back to normal. The engine runs smoothly even on the coldest mornings now. No more issues with heat not working or rough running, the fix completely resolved all the symptoms. Have not experienced any other temperature control problems in the past 6 months since the repair. The HVAC system works exactly as it should, with proper heat output from the start. Just make sure to use a shop that really knows their way around Audi electrical systems, as properly diagnosing and fixing these heater components requires specific expertise.

Thanks for all the helpful feedback everyone. Finally got my A4 fixed last week and wanted to share my experience. Took it to a different shop that specializes in Audi electrical work. They confirmed the faulty PTC heater diagnosis and found some corroded wiring in the heating system too. Total repair cost was 420 Euro, a bit more than expected but worth it. The HVAC system now works perfectly and cold starts are smooth. My fuel consumption dropped back to normal levels too. Temperature control is spot on, even on cold mornings. The mechanic explained everything clearly and showed me the old heating element, it was completely burnt out. Glad I switched shops. The new place charged fair prices and did quality work. If anyone else faces similar cold start issues, definitely get the PTC heater checked out first.