SQ8 TDI Alternator Issues Causing Multiple Failures

I had a similar alternator issue with my 2018 Q7 TDI last winter. Having some experience with car electronics, I initially thought it was just a serpentine belt problem, but the symptoms matched yours exactly, dimming lights, weak starts, and charging system warnings. The battery voltage was dropping while driving, which is a clear sign of alternator problems. After monitoring the charging system with a multimeter, it confirmed the alternator was failing to maintain proper voltage. The repair involved: Complete alternator replacement, New serpentine belt installation, Battery system reset, Electrical system diagnostic Total cost was 960 Euro for parts and labor. The workshop verified the fix by testing the charging system output under various loads. After replacement, all electrical issues disappeared completely. To better assist with your case, could you share: Current mileage, Any recent electrical modifications, Whether battery voltage has been tested, If you notice the issues more during cold starts, Specific warning messages on the dash These details would help determine if your symptoms truly match the alternator failure pattern I experienced.

Latest service completed at 159209KM, but these alternator symptoms started shortly after. The voltage drop occurs primarily during acceleration, and I checked the battery output showing inconsistent readings. Using a multimeter, I measured fluctuating voltage between 12.1V and 13.8V while running, indicating the charging system is definitely compromised. The starter motor still engages properly, but requires more cranking time than usual. Workshop diagnosed potential voltage regulator failure within the alternator unit itself. Good to know about your successful repair outcome, sounds like my symptoms align perfectly with your experience. Currently waiting on parts availability before booking the repair. Did your workshop mention if this is a common failure point on VAG diesel engines?

Thanks for the voltage readings, they definitely confirm what I experienced with my Q7. Those fluctuating numbers between 12.1V and 13.8V are almost identical to what my alternator was producing before failure. During my alternator replacement, the technician mentioned the voltage regulator failure is actually fairly common in these engines after 150000km. The charging system tends to show intermittent behavior before complete failure. My alternator issue also started with longer cranking times and voltage drops during acceleration. The engine misfire and reduced power symptoms appeared as the problem worsened, since the engine management system reduces performance when it detects unstable electrical supply. A few tips from my experience: Have them check the alternator bearings during replacement, Request testing of the entire charging system post-repair, Consider a battery load test even though its new, Keep track of any stored error codes The complete alternator replacement resolved all electrical gremlins in my case. The stable voltage restored proper engine performance and eliminated those frustrating warning lights. Just ensure your workshop uses OE-spec parts for the repair.

I appreciate all the detailed info about your repair experience. The voltage readings from your car match mine exactly, so this confirms my suspicions about the alternator. My situation seems to be following the same failure pattern, starting with the voltage fluctuations and progressing to performance issues. Good point about the 150000km being a common threshold for voltage regulator problems in these engines. Given my mileage is right around there, this makes perfect sense. The car won't start as easily now, but knowing the alternator replacement fixed your charging system issues completely gives me confidence about proceeding with the repair. I will definitely have them check the alternator bearings and test the entire charging system once the new unit is installed. I have already documented all the error codes to share with the workshop. Since this seems to be a known weak point, I will insist on OE-spec parts to avoid any repeat failures. Thanks for the comprehensive breakdown of your repair process. This gives me a clear picture of what to expect when I take it in for the alternator replacement. At least I know I am not chasing an intermittent electrical gremlin and there is a definitive fix available.