VW TDI Cold Start Issues & High Fuel Consumption Fix

I had a very similar issue with my 2004 VW Passat TDI. Having some experience with diesel engines, I recognized these symptoms immediately, especially the cold start problems and HVAC system issues. The electric auxiliary heater was indeed defective in my case. The symptoms matched exactly what you describe, increased fuel consumption, problematic cold starts, and heating system not performing properly. The PTC heater element had failed, which is common in these diesel engines as they rely heavily on the auxiliary heating system during cold weather. After diagnosis, my workshop replaced the heating element and performed a system reset. Total cost was 350€ for parts and labor. Since the repair, the cold starts have been smooth, fuel consumption returned to normal, and the heating system works perfectly again. To provide more specific advice for your case, could you share: Current mileage, Whether you notice any specific error codes, How long the symptoms have been present, If the heating performance varies with engine temperature, Whether you hear any unusual sounds from the heater system These details would help determine if your issue is identical to what I experienced with my Passat.

Just had my service last week and they ran diagnostics. Getting error code P0670 which points to the glow plug control module. Cold air issues are definitely worse when the engine is cold, but the heating system seems to work better once warmed up. No unusual sounds from the heater. The electrical fault in the heating system is causing the engine to compensate by injecting more fuel during cold starts. After checking my fuel logs, Im burning about 15% more diesel compared to last month. Heat not working properly during the first 10 minutes of driving is particularly annoying in cold weather. The service center quoted 420€ for full diagnosis and repair, including parts. Just wondering if thats reasonable before I commit to the work.

Thanks for providing those additional details. Your error code P0670 confirms what I suspected, its definitely related to the glow plug control system, just like my Passat issue. The 15% increase in fuel consumption matches my experience almost exactly. The 420€ quote seems reasonable considering current parts prices. For comparison, my 350€ repair was done two years ago, and parts costs have increased since then. The full diagnostic work they are including makes the price fair. The behavior you describe with the heating system working better after warm-up is typical for a failing PTC heater system. When I had mine fixed, the blower motor was actually fine, but the heater control module needed replacement along with the glow plug module. Since you mentioned the cold air problems are worse during initial startup, this strongly suggests the auxiliary heating system isnt providing enough support during the critical warm-up phase. After my repair, this cold-start hesitation disappeared completely. Id recommend going ahead with the repair. The fuel savings alone will help offset the cost, and proper heater operation during those first 10 minutes makes a huge difference in comfort.

Thanks for the input. After reading through the responses and comparing symptoms, I feel much more confident about proceeding with the repair. The HVAC system issues and cold start problems match exactly what others experienced, and the heater repair costs seem to be in line with current rates. Im going to schedule the work for next week. The 420€ investment makes sense, especially considering Im wasting money on extra fuel consumption right now. The electrical fault diagnosis pointing to the glow plug control module combined with the PTC heater issues seems to explain all my symptoms. Will update once the repair is done to confirm if it resolves both the cold start problems and heating performance. Really helpful to hear from others who dealt with similar issues in their TDIs.