Smart Fortwo Charging Issues Fixed By Replacing Regulator

Had the exact same problems with my Smart Forfour from 2008. Being somewhat experienced with basic car maintenance, I first checked the battery terminals for corrosion and loose connections, but the issues persisted. After testing the battery health at home with a multimeter, I noticed significant voltage drops while the engine was running. The readings were jumping between 11V and 13V, when they should stay steady around 14V. Took it to a workshop where they diagnosed a faulty voltage regulator that was causing the alternator to charge inconsistently. The entire repair, including parts and labor, cost me 290€. The symptoms disappeared completely after the fix. The technician explained that these electrical issues are quite common in this model range and usually stem from either the voltage regulator or the alternator itself. What engine size does your Fortwo have? Have you noticed if the problems get worse when using multiple electrical accessories at once? This information could help determine if you are facing the same issue. Also, when was the last time your battery was replaced? A battery health test would be a good starting point before diving into more complex charging system repairs.

Last service was at 84000 KM, only about 2 months ago. After reading your experience, I checked my battery terminals for any obvious issues and measured the battery voltage. Getting similar inconsistent readings between 11V and 12.8V while running. The battery is fairly new (replaced 8 months ago), which made me suspect the charging system rather than the battery itself. The electrical problems definitely get worse when running multiple accessories, headlights, AC, and radio together make the voltage drop noticeably. I have the 599cc engine. This really sounds similar to your voltage regulator issue. Will have it properly diagnosed based on your feedback rather than just throwing parts at it. The 290€ repair cost seems reasonable compared to potentially replacing the whole alternator.

Having gone through this exact issue with my Smart Forfour, your voltage readings and symptoms match my experience perfectly. The inconsistent voltage between 11V and 12.8V while running is a classic sign of a failing voltage regulator, especially since your battery is only 8 months old. The way your electrical problems worsen with multiple accessories matches what I experienced too. The voltage drop under load is a telltale sign of the charging system not keeping up. The 599cc engine uses the same basic charging system components as my Forfour did. Since your battery health is likely still good given its age, replacing just the voltage regulator should resolve the issue. When my regulator was replaced, the workshop also performed a full charging system diagnostic to ensure the alternator itself was functioning correctly. The repair cost I mentioned earlier covered both the diagnosis and the fix. Given current parts prices have stayed relatively stable, you should expect similar costs. Make sure they test the alternator output after the repair, in my case, the voltage stabilized at a proper 14V with the new regulator installed. Did you notice if the battery warning light on the dash comes on intermittently while driving? This was another symptom I forgot to mention in my previous response.

Thanks for sharing those test results. Since my battery is relatively new, I feel more confident now that the voltage regulator is the likely culprit. You are right about the battery warning light, it does flicker occasionally, especially when idling. The voltage readings match your experience exactly, and the way the electrical system struggles with multiple accessories really points to a charging system problem rather than the battery itself. This helps narrow down the diagnosis significantly. Going to book it in for a proper diagnostic test this week and have them focus on the voltage regulator first. The alternator power supply seems to be inconsistent just like in your case, so hopefully replacing the regulator will stabilize the voltage output. Will make sure they do a complete charging system check and verify the alternator output returns to proper levels after the repair. The 290€ repair cost seems fair for the work involved. Much better than guessing and potentially wasting money on unnecessary parts. Really appreciate you sharing your workshop experience, it helped avoid a lot of potential trial and error with unusual part replacements.