VW Beetle Won't Start: Terminal 15 Voltage Mystery

I had a very similar issue with my 2014 VW Golf. With some experience working on VWs, I can share what worked in my case. After facing starting problems, my voltage drop tests also showed similar symptoms. The starter solenoid wasnt receiving proper voltage despite a healthy battery. Initially suspected the battery terminal connections, but like yours, they were fine. Took it to my regular workshop where they traced it to corroded wiring connections near the fuse box. The main power supply cable had developed microscopic breaks in the insulation, leading to intermittent connection issues. The circuit break was happening between the ignition switch and starter solenoid. The fix involved replacing a section of the wiring harness and cleaning all connection points. Total repair came to 95€ including diagnostics. Car has been starting perfectly since then. Before suggesting more specific solutions, could you share: Does the issue happen consistently or intermittently? Are there any other electrical symptoms like flickering lights? Have you checked all fuses in both the main fuse box and secondary locations? What specific error codes is the car storing? This information would help determine if youre dealing with the same root cause or if theres something else going on.

Last service was performed at 41197km and the mechanic found a poor ground connection at the starter circuit. The relay switch was clicking but not engaging properly due to the wiring harness degradation between the ignition switch and the fuse box. The voltage drop across this section was significant, preventing proper current flow to the starter solenoid. This matches several reported cases where corrosion at key connection points causes similar starting issues. A complete circuit test revealed several weak points in the ground straps and main power feed. The fix involved replacing the affected wiring sections and cleaning all terminal connections. Since the repair, the starting issue has not returned. Total repair cost was 280€ for parts and labor combined. Could you confirm if you hear the characteristic relay click when turning the key? This would help isolate whether the ignition switch itself is the culprit or if the issue lies further downstream in the circuit.

Thanks for sharing the details about your repair. Yes, I also heard that distinct relay click in my Golf before the fix, which is what initially made me suspect the wiring rather than the relay switch itself. The poor ground connection you found matches my experience, these VW models seem prone to developing corrosion at critical ground points in the starter circuit. The voltage drop pattern you described is nearly identical to what my mechanic discovered. When they tested my car, the power supply was fine at the battery but showed significant loss between the ignition switch and fuse box connections. Those microscopic breaks in the wiring harness insulation I mentioned earlier were allowing moisture to create corrosion points. One thing to watch for, even after fixing the main issue, make sure they thoroughly check all the ground straps. In my case, they found a secondary ground connection that was also starting to degrade. Addressing both prevented the problem from recurring. The repair cost difference makes sense since my fix only needed partial harness replacement, while yours required more extensive work. The critical factor is ensuring all the connection points are properly cleaned and sealed to prevent future corrosion.

The relay switch click is definitely happening when I turn the key, very similar to what you described. After getting more details about your repair, Im confident were dealing with the same underlying issue with the wiring harness. Looking at my service records, the starting problems began occurring right around the 40000km mark. The coincidence with your timing and symptoms is striking, especially the voltage drop pattern between the ignition switch and the fuse box. My mechanic is scheduled to inspect it tomorrow. Will ask them to focus on checking the power supply connections and ground points you mentioned. The degraded insulation causing corrosion makes perfect sense given the symptoms. One question, did your repair also involve any work on the ignition switch itself, or was it purely focused on the wiring harness and ground connections? The parts quote Im looking at includes both, but based on your experience, it sounds like the switch might not be necessary. The 280€ estimate seems reasonable if it includes a complete circuit inspection and harness replacement. Better to fix it properly now than risk further electrical issues down the line.