SQ7 Power & Electrical Failures Point to Failing Alternator

Faced nearly identical symptoms with my S5 (2020) last winter. The battery low warning was the first sign, followed by dimming headlights and sluggish starter motor operation. Initial voltage drop testing confirmed the alternator was only producing 11.2V instead of the required 13.5-14.5V. The root cause was a worn-out voltage regulator inside the alternator assembly. While some shops suggest replacing just the regulator, a complete alternator replacement was necessary in my case due to additional bearing wear. The repair involved: Removing the serpentine belt, Testing the belt tensioner (which was also showing wear), Replacing the alternator assembly, Installing a new belt tensioner, Performing a full charging system diagnostic This was a serious repair requiring about 4 hours of labor. The car would eventually have stopped running completely as the battery would no longer maintain sufficient charge. The symptoms you describe match alternator failure exactly, when the charging system fails, all electrical components suffer and engine performance deteriorates since modern engines rely heavily on electrical systems. Post-repair testing showed proper charging at 14.2V and all systems returned to normal operation.

Thanks for sharing such detailed info about your alternator replacement experience. Those voltage readings definitely confirm what I suspected with my SQ7. The charging system symptoms sound identical, my battery drains quickly and electrical systems are getting weaker by the day. Did you remember roughly what the total repair cost came to? And has everything been running smoothly since the fix? Just want to make sure no other related issues popped up after the alternator work was done. I will probably need to take mine in soon before the car won't start at all. The engine misfire and power loss are getting worse, especially during cold starts.

Glad I could help. The Generator repair on my S5 ended up costing 960 Euro total, including the new tensioner and serpentine belt. It was worth every cent though, as the car has been running flawlessly for months now. The car electronics are all working perfectly, no more dim lights, battery warnings, or starter motor issues. The repair completely resolved those worrying symptoms you mentioned. My voltage now consistently stays at the correct level, and cold starts are as smooth as when the car was new. If your symptoms match what I experienced, getting it fixed sooner rather than later is smart. When the charging system fails, it can leave you stranded when the car won't start, usually at the most inconvenient time. The generator repair restored full power to all systems, and I haven't had a single electrical problem since. Just make sure they do a full charging system diagnostic afterward to confirm everything is operating within spec.

I took my SQ7 to the shop yesterday after all the helpful advice here. The mechanic confirmed it was indeed an alternator issue, output was only at 11.4V. They did a complete alternator replacement along with the belt tensioner and serpentine belt while they were in there. Total cost came to 1150 Euro for parts and labor, which seemed fair given the work involved. The car started right up this morning with no battery warnings. All the electrical systems are working perfectly now, bright lights, strong starter motor, and the engine runs smoother than it has in weeks. Really glad I got this fixed before ending up stranded somewhere. The voltage drop was apparently pretty severe and the mechanic said the battery was close to being damaged from constant undercharging. Thanks again for helping me diagnose this alternator issue correctly before taking it in.