Audi S1 Cold Start Issues Point to PTC Heater Failure

Had exactly this issue with my 2012 Audi S3 a few months back. I have some experience working on cars but the electrical fault in the heating system was beyond my skills. The symptoms match perfectly, rough cold starts, increased fuel consumption, and the HVAC system not performing right. The check engine light was my first warning sign too. The root cause turned out to be a defective electric auxiliary heater. Took it to a workshop where they ran a full diagnostic. The heating system needed attention as the auxiliary heater was failing to pre-heat properly during cold starts. They replaced the PTC heater element and recalibrated the system. Total repair cost was 350 Euro and the car was ready next day. Now everything works perfectly, cold starts are smooth, heat works great, and fuel consumption is back to normal. Could you share some additional details about your S1: Are there any other warning lights besides check engine? Does the heat not working issue occur only during cold starts? Have you noticed any specific engine sounds during cold starts? When was your last full service? This info would help determine if your issue is identical to what I experienced.

Thanks for the detailed reply. According to my service records from last month at 75344 KM, they did check the heating system but found no issues back then. No other warning lights are present besides the check engine light. The cold air problem happens consistently during cold starts, and the engine makes a slight rattling noise for about 30 seconds after startup. The temperature control seems particularly unreliable during the first few minutes of operation. The heating element issue you described sounds very similar to my situation. Did your mechanic mention if this is a common problem with these engines? I might get it checked at a workshop this week.

Thanks for the additional details. Your symptoms are getting more similar to what I experienced with my S3. That rattling noise during cold starts was exactly what I heard too, it is often a telltale sign of the PTC heater malfunction affecting the engine warm-up phase. Even though your service records show no issues last month, the heater repair was likely not part of their standard checks. The temperature control problems you describe, combined with the rattling noise and poor cold starts, strongly point to a failing heating element. In my case, the workshop confirmed this is a somewhat common issue on these engines, especially as they age. The PTC heater tends to deteriorate gradually, which explains why the problem might not have been obvious during your last service. The electrical fault typically shows specific error codes related to the auxiliary heating system. When they diagnosed my car, they found multiple codes pointing to the heater element malfunction. If you plan to get it checked, request a specific diagnostic of the auxiliary heating system. Based on my experience, waiting too long can lead to increased strain on other engine components and worse fuel consumption.

Thanks for sharing those insights about the PTC heater problems. After hearing about your similar experience, I am more confident that my heating system needs attention. The rattling noise and cold start issues do match up exactly with what you described. I have scheduled an appointment at a workshop for next week. I will make sure to ask them to specifically check the auxiliary heating system and look for those error codes you mentioned. The 350 Euro repair cost seems reasonable if it fixes all these issues, the increased fuel consumption alone is probably costing me more in the long run. Really helpful to know this is a common problem with these engines. Makes sense why the regular service check might have missed it. Will update once I get the diagnostic results and know what needs replacing. Hopefully its just the heater element like in your case and nothing more serious.