VW Touran Won't Start: Terminal 15 Circuit Issue Fix

Having worked on a 2015 VW Tiguan with a similar starting issue, I can share my experience as someone with moderate automotive repair knowledge. The symptoms were nearly identical, engine would crank but not fire up. After multiple attempts at diagnosis, it turned out the wiring harness had developed a fault causing voltage drop in the ignition circuit. The starter solenoid was getting power, explaining why it would crank, but the circuit break in the harness was preventing proper power supply to the ignition system. My workshop found damaged wire insulation near the steering column that was causing intermittent connection issues with Terminal 15. The total repair cost was 95€, which covered replacing the affected section of the wiring harness and testing the circuit. To better assist with your specific case, could you share: Engine size and type, Whether you get any specific error codes, If the problem occurs only when the engine is hot or cold, If you notice any other electrical issues This information would help determine if your issue matches the common Terminal 15 problems seen in this engine family. The workshop suggested checking all ground connections and the ignition switch wiring before replacing any major components, as these are often overlooked but common failure points in the ignition circuit.

Last service was completed at 55000km. Let me add my experience to confirm similar symptoms in my case. The ignition switch started showing intermittent behavior before complete failure. I noticed the battery terminal connections were solid, but the problem persisted. My mechanic found that the wiring harness near the steering column showed signs of wear, affecting the power supply to Terminal 15. A circuit break diagnosis revealed voltage inconsistencies when turning the key. The workshop also found corroded pins in the main ignition relay that needed cleaning. Total repair ended up at 210€ including parts and labor. Initially suspected the starter motor but testing confirmed the issue was in the ignition circuit itself. The intermittent nature of the problem made diagnosis tricky until proper voltage testing was done at various points in the system. Would be interested to know if your symptoms get worse with engine heat or after long drives.

Thanks for sharing those details about your ignition circuit issues. The symptoms in your case match what I experienced with my Tiguan before getting it fixed. My starting problems definitely got worse with heat, especially after long highway drives. The ignition switch would sometimes need multiple attempts before engaging properly once the engine bay was hot. The power supply would seem to cut out intermittently, which the workshop later traced to heat-affected wiring near the fuse box. One thing I noticed during diagnosis was that wiggling the wiring harness near the steering column would sometimes temporarily restore proper function. This helped pinpoint the circuit break location. The workshop found that heat cycling had caused the wire insulation to become brittle and crack in that area. After fixing the wiring and cleaning the ignition relay terminals, they also applied dielectric grease to prevent future corrosion issues. The repair has held up well for over 18 months now with no recurrence of starting problems. Based on the similar repair costs and symptoms, it sounds like we had nearly identical issues with the Terminal 15 circuit. The heat sensitivity is a classic sign of wiring problems rather than component failure.

Good to know the heat was a factor in your case too. Thanks for confirming the connection between temperature and starting issues. My mechanic just called with an update. They traced the intermittent voltage drop to a damaged section of wiring harness where it passes through the firewall. The protective sleeve had worn through, exposing wires to heat and moisture. The starter solenoid was getting enough power to crank, but the ignition switch circuit was compromised. Testing also revealed a weak ground connection at one battery terminal that was contributing to the problem. The fuse box connections all checked out fine, but they found some corrosion on the main power distribution points that needed cleaning. Parts and labor estimate is now at 180€, slightly better than my initial repair. They recommend replacing the affected wiring section and adding extra protection against heat damage. Will update once the work is complete to confirm if this fully resolves the starting issues. The consistent symptoms between our cases, especially the heat sensitivity and Terminal 15 circuit problems, gives me confidence they found the root cause. Now I just hope the repair holds up as well as yours has.