Alfa Battery Sensor Issues Causing Starting Problems

As someone with some experience working on Alfas, I faced an almost identical issue with my 2003 Alfa 156 JTD. The symptoms you describe match exactly what I encountered, weak cranking and flickering lights pointed to battery-related problems. After initial battery testing showed normal readings, my workshop identified a faulty battery sensor as the root cause. The voltage sensor was misreporting battery charge levels to the car's systems, causing erratic electrical behavior. The repair involved replacing the battery sensor unit, which solved both the starting issues and flickering lights completely. Total cost was 315 Euro, including diagnostic time and parts. To provide more specific guidance for your case, could you share: Current mileage on your 159, When the battery was last replaced, Whether you notice these issues more during cold starts, If any warning lights appear on the dashboard, Results from your battery voltage readings These details would help confirm if your situation matches what I experienced with the faulty sensor. The battery sensor replacement is a common fix for these symptoms in this engine family, but its best to verify with complete information.

Last service done at 54932 KM shows everything fine with alternator and general electronics. The battery charge readings were within normal range, but battery sensor symptoms persist even after cleaning connections. I ran additional voltage tests as suggested, getting inconsistent readings between 11.2V and 14.4V when idling. Cold starts are definitely worse. No dashboard lights besides occasional battery warning that comes and goes. Battery is only 8 months old with proper capacity. Reaching out to get more repair insights before booking workshop time.

Based on those voltage readings and your description, this definitely mirrors what I experienced with my 156. The fluctuating voltage readings between 11.2V and 14.4V are particularly telling, these inconsistent readings were exactly what led to diagnosing my faulty battery sensor. The fact that your battery is only 8 months old further supports that the battery sensor is likely the culprit. In my case, the sensor was providing incorrect battery charge information to the engine management system, causing similar erratic voltage patterns. A properly functioning voltage sensor should maintain stable readings around 13.8-14.2V at idle. These wild swings youre seeing match the behavior I saw before replacing my sensor unit. The intermittent battery warning light also matches my experience, this happens when the sensor sends conflicting battery health data to the system. With cold starts being notably worse, this strengthens the case for a sensor issue. The battery maintenance history and age rules out actual battery problems, leaving the sensor as the most probable cause. Would strongly recommend getting the sensor replaced based on how closely this matches my repair experience. The fix completely resolved these issues on my car, and the symptom pattern is nearly identical.

Thanks for all the detailed feedback about the voltage readings and cold start behavior. This really helps confirm what I suspected about the battery sensor being the likely culprit. Those fluctuating voltage readings between 11.2V and 14.4V definitely seem problematic, especially since my battery itself is practically new. The low voltage during cold starts combined with the intermittent battery warning matches exactly what others described before fixing their sensor issues. Knowing that replacing the battery sensor resolved similar symptoms for other Alfa owners gives me confidence about moving forward with the repair. Going to schedule the sensor replacement next week. The alternator tests and general electronics all checking out normal during my last service further supports that the battery sensor is the root cause. Will update once the repair is done, but feeling much better about targeting the voltage sensor rather than replacing a perfectly good battery or chasing other electrical gremlins.