VW Transporter's Voltage Nightmare Wreaks System Havoc

My 2012 VW Crafter had very similar electrical issues. Having some experience with car electrical systems, I initially thought it was just the battery, but it turned out to be more complex. The voltage regulator in the alternator was causing irregular charging patterns, which damaged the car battery. The electrical issue was causing unusual system failures and ECU errors, just like yours. After proper diagnosis at the workshop, they found the alternator was outputting inconsistent voltage. The repair involved: Testing the alternator output, Replacing the voltage regulator, Installing a new car battery, Clearing all fault codes, Testing circuit protection systems Total cost was 290€ and it fixed all the unusual electrical failures. Before suggesting specific solutions, could you share: Battery age and voltage readings if you have them, Whether the alternator warning light comes on, If you notice dimming headlights at idle, Current battery voltage while running This would help determine if your Transporter is facing the same alternator failure pattern I experienced.

Latest service was at 77000km and the alternator warning light stays off during normal operation. I checked the battery voltage as suggested, it reads 14.8V while running and drops to 11.9V at idle. The headlights do dim slightly at idle, especially with AC running. These readings seem to confirm alternator failure symptoms similar to those described. The voltage spikes above 14.5V suggest issues with the voltage regulator, while the significant drop at idle points toward inconsistent charging patterns. What troubles me is that the circuit protection systems dont seem to be managing these voltage fluctuations properly. The battery is only 8 months old, so premature wear from overvoltage could explain its weak performance.

Thats exactly the same voltage pattern I saw in my Crafter before replacing the regulator. 14.8V is definitely too high during operation, these vans are designed to run at 13.8-14.2V. The drops to 11.9V at idle are classic symptoms of a failing voltage regulator not maintaining proper circuit protection. The high voltage spikes are likely causing the multiple fault codes and stressing various electronic components. My van showed similar power surge patterns before the fix, especially that telltale drop at idle with AC load. Regarding your 8-month-old battery, mine was also fairly new when this happened. The constant overvoltage from the alternator damaged its cells prematurely. After fixing the alternator, my new battery has lasted 2 years without issues. Based on the identical symptoms, I strongly recommend having the alternator tested. The voltage regulator replacement fixed all my car ECU errors and unusual system failures. The repair cost will be worth preventing further electrical component damage from these voltage fluctuations. One tip: keep a log of voltage readings at different RPMs. This helps the workshop diagnose the exact charging system behavior and verify the fix worked properly.

Thanks for sharing those voltage readings, theyre quite revealing. The 14.8V running and 11.9V idle readings match the symptoms you described, and Im glad to have more specific data to compare with your experience. The alternator problems you faced with your Crafter sound identical to what Im dealing with. The combination of high voltage during operation and significant drops at idle, plus the dimming headlights with AC load, really points to voltage regulator failure as the root cause. Ill definitely get the alternator tested soon. Its reassuring to hear replacing the voltage regulator and battery resolved your electrical gremlins completely. The fact your new battery has lasted 2 years is particularly encouraging, since my 8-month-old one is already showing signs of stress from the overvoltage issues. Ill start logging voltage readings at different RPMs as suggested. This should help pinpoint the exact charging system behavior and ensure any repairs fully resolve the car ECU errors and unusual failures. Better to fix it now than risk more extensive electrical component damage. Thanks for sharing such detailed repair information, its been incredibly helpful in understanding what Im dealing with.