VW Fox Diesel Starting Failure Linked to Terminal 15

Based on similar symptoms with my 2013 VW Polo TDI, this sounds like a starter solenoid issue combined with a faulty relay switch. The car won't start problem often relates to the power distribution between terminal connections. The repair required removing the starter motor assembly to access the solenoid. The main issue was corrosion on the battery terminal connections and a damaged circuit break in the relay system. These components typically deteriorate after 60000km, especially in diesel engines. The root cause was a loose connection between the starter solenoid and the main power circuit. When testing the ignition, we found intermittent power supply to Terminal 15, indicating a classic relay switch failure. This is considered a serious electrical system issue that can prevent the engine from starting completely if left unaddressed. The repair involves: Testing the starter solenoid, Checking all relay switches, Cleaning battery terminal connections, Replacing corroded wiring, Installing new ignition relay Consider getting the starter motor assembly checked first, as this is often the primary cause rather than just the Terminal 15 connection.

Thanks for sharing your experience. Had almost identical issues with my Fox last winter. Fixed it after replacing the starter solenoid and cleaning the battery terminals. Voltage drop was causing intermittent starting problems. Just curious, how much did the full repair end up costing you? Any other electrical issues pop up since the fix? My power supply has been stable after the repair, but wondering if I should keep an eye out for anything specific.

Got an update on that repair situation. After seeing the mechanic again, they found that Terminal 15 ignition positive was indeed interrupted, just like we suspected. The fix was pretty straightforward, they repaired the cable connection that was causing the component failure. Total cost came to 95€, which was actually less than expected for an electrical system repair. Since fixing the power supply issues, the car has been running perfectly. The ignition switch fires up every time now, and all the electrical systems are working as they should. The mechanic also did a full check of the fuse box and other circuit breaks while they were at it, just to be thorough. One thing I learned from this, keeping the battery terminal connections clean really does make a difference in preventing these kinds of problems from coming back. Haven't had any electrical gremlins since the repair, but I still check the connections regularly just to be safe. The diagnostic tool they used pinpointed the exact issue with the Terminal 15, which saved time and money compared to my previous repair attempts. Sometimes having the right equipment makes all the difference.

Had to update everyone on my repair journey. Finally took it to a different mechanic who actually knew what they were doing. They ran a proper diagnostic and found the issue right away, a worn out starter solenoid causing the no-start condition. The wiring harness near the starter was also showing signs of wear, so they replaced that section while they were in there. Total bill came to 320€ including parts and labor. Way less than what the first shop wanted to charge for replacing parts that werent even broken. The car starts perfectly now. First click, every time. They also cleaned up some corrosion in the fuse box they found during inspection. Really glad I got a second opinion instead of throwing more money at the first shop. A good mechanic who actually diagnoses the problem instead of just replacing parts makes all the difference. Lesson learned, when the car wont start, find someone who knows how to properly test the electrical system first.