Smart Roadster Battery & Alternator Warning Signs Appear

I had a very similar alternator issue with my 2003 Smart Coupe. With some experience working on these small city cars, I recognized the symptoms right away, voltage drop while driving, dimming lights, and battery low warnings. My workshop first tested the charging system and confirmed the alternator was failing to produce sufficient power. They did a complete diagnostic check which revealed: Alternator output was well below specs, No issues with battery or starter motor, All connections and wiring were intact, No engine misfire or related problems The repair involved: Removing and replacing the alternator unit, Testing the new alternator output, Checking/cleaning all electrical connections, Full system diagnostic after repair Total cost was 960€ including parts and labor. The fix completely resolved all symptoms, proper charging, normal brightness lights, and reliable starting. What engine variant does your Roadster have? Also, have you noticed any additional symptoms like rough idling or electrical issues with other components? This information would help determine if your situation matches what I experienced. Pro tip: While waiting for repairs, avoid short trips and using electrical accessories unnecessarily, as this can strain the weakened charging system.

Last service was at 130000 KM, and currently showing 133610 KM. Since the initial repair assessment, I have noticed other car electronics acting up, particularly the power windows becoming sluggish. Ran a voltage test at home which confirmed significant voltage drop when running electrical components. The serpentine belt looks OK visually, but I have noticed a slight squealing noise on cold starts. This makes me wonder if belt tension could be contributing to the alternator issue. The battery terminals are clean and tight, but battery low warnings persist. Will get it checked properly next week and update the thread with findings.

Thanks for those additional details about your Smart Roadster. The symptoms you describe match exactly what I experienced with my car before the alternator replacement. The squealing noise during cold starts combined with the voltage drop is a classic sign of charging system problems. In my case, even though the belt looked fine, it had actually stretched slightly, reducing alternator efficiency before the unit completely failed. After fixing my alternator, I learned these issues often follow a pattern: First, electrical components act sluggish (like your power windows), Then car electronics start showing unusual errors, Finally, the charging system fails completely My car started showing issues around 135000 KM, very close to your current mileage. The workshop also found the belt tensioner had worn, affecting the alternator drive. They recommended replacing both components together. A weak charging system can cause so many seemingly unrelated problems. My power windows and central locking went weird first, then other car electronics started failing intermittently. Once the new alternator was installed, everything worked perfectly again. Would be interested to hear what your workshop finds during the diagnostic check next week. Sounds very similar to what my car exhibited before repairs.

Thanks everyone for the helpful input on my Smart Roadster alternator issue. After doing some basic voltage testing and seeing all these similar experiences, I'm more confident it's the charging system causing the problems. The serpentine belt squeal and voltage drop match what others experienced. My sluggish power windows and electrical gremlins definitely point toward alternator issues, especially given the mileage. Going to have the workshop do a full charging system diagnostic next week. Will make sure they check both the alternator and belt tensioner since several people mentioned these often need replacing together. Based on the repair costs shared, looking at around 900-1000€ for parts and labor, which helps with budget planning. For now, following the advice to minimize short trips and electrical accessories until the repair is done. Will update once I get the workshop diagnosis and repair completed.