VW Beetle's Mystery Electrical Issues: Charging Solutions

I had a very similar charging system problem with my 2017 VW Golf last winter. As someone with basic car maintenance experience, I first thought it was an alternator issue since the symptoms matched, flickering lights and inconsistent electrical system behavior. After taking it to a workshop, they performed a complete diagnostic of the power supply system. Despite having a relatively new battery like yours, it turned out the battery was heavily discharged and ultimately defective. The workshop tested both the alternator and battery health, finding the charging system was actually working fine but the battery was not holding charge properly. The total repair cost was 290€ including diagnostics and a new battery replacement. Since then, the electrical systems have worked flawlessly with no more starting issues or warning lights. Before suggesting specific checks for your Beetle, could you share: Current battery voltage reading if you have a multimeter, Whether the charging system warning light stays on continuously or only appears occasionally, If you notice the issues more during cold starts or after the engine is warm, Whether any other warning lights appear on the dashboard This information would help determine if your case matches what I experienced or points to a different root cause in the charging system.

Thanks for sharing your experience. At 79382km and recent service last month, my symptoms do sound quite similar. I checked the battery voltage which reads 12.1V when the engine is off and only rises to 13.2V while running, seems low for a healthy charging system. The warning light is definitely intermittent, mostly appearing during acceleration or when multiple electrical accessories are running. I notice the voltage drop is worse during cold starts, but the flickering continues even after the engine warms up. No other warning lights on the dashboard. Based on your experience, I will have the voltage regulator and alternator output tested along with a full battery health check. Really helpful to know that even a relatively new battery could be the culprit despite showing classic alternator issue symptoms. Would you recommend having the battery terminals cleaned and checked for corrosion as part of the diagnostic process?

Based on those voltage readings, your situation does sound nearly identical to what I experienced. The battery voltage while running should be between 13.8V-14.4V with a properly functioning charging system, so 13.2V definitely indicates an issue. When my Golf had similar symptoms, cleaning the battery terminals did help temporarily but didnt resolve the underlying problem. The voltage regulator in the alternator was actually working correctly, it was the battery that wasnt accepting or holding the charge properly despite being relatively new. Those cold start issues combined with voltage drop under load strongly suggest a failing battery. Even new batteries can be defective or get damaged by repeated deep discharge cycles. My repair invoice shows they tested: Battery health under load, Alternator output at various RPMs, Voltage regulator function, Main power supply connections The complete diagnostic process cost 60€ but was credited toward the repair. Given your voltage readings match my previous issue almost exactly, I would start with a professional battery load test before replacing more expensive charging system components. Make sure to save your voltage readings to show the technician, those numbers help confirm the diagnosis and potentially speed up the troubleshooting process.

Thank you everyone for the input. After getting these voltage readings, I feel more confident about the likely diagnosis. The electrical problem appears to be related to low voltage from a potentially defective battery, even though its relatively new. I scheduled an appointment at the repair shop for tomorrow. Based on the feedback here, I will ask them to perform: Full battery health check, Load testing to verify charging capacity, Test the voltage regulator and alternator output, Inspect and clean all battery connections The readings of 12.1V at rest and 13.2V while running seem to confirm a charging system issue. Really helpful to know that even a 6-month-old battery could be the root cause rather than automatically assuming its an alternator problem. Will update once I get the diagnosis. The quoted diagnostic fee of 65€ seems reasonable given the thorough testing needed to properly identify electrical problems in these systems. Thanks again for helping narrow down the most likely cause before heading to the shop.

Hello everyone, how do you find the designation of the control unit in this supposedly good app? I mean the VW number, e.g., 1k234..... Thank you very much

(community_translated_from_language)