High Alternator Voltage Causing Q7 Electrical Failures

Had the exact same symptoms on my A6 2018 3.0T last winter. The power surge issues started showing up as unusual warning lights, slow cranking, and electrical glitches across multiple systems. The root cause was a failing voltage regulator inside the alternator, which was pushing excessive voltage through the car electronics. This overcharged the battery while driving but paradoxically left it weak for starting. The high voltage readings also triggered various ECU protection modes. The fix required: Complete alternator replacement (the voltage regulator is not serviceable separately), New AGM battery since the old one was damaged by the overvoltage, Full system diagnostic reset after repair It was a serious electrical issue that could have damaged more expensive components if left unchecked. The alternator failure caused the voltage to spike above 15V at times, which risks damaging sensitive electronic modules. Worth checking: Battery voltage at rest and while running, Alternator output voltage across different RPMs, Ground connections and main power cables for corrosion, Fuse box for any signs of heat damage Get these verified before component replacement to ensure accurate diagnosis.

Thanks for sharing your experience. Dealing with almost identical circuit protection warnings and alternator failure symptoms on my 2020 Q7 right now. The car electronics going haywire and unusual system faults match exactly what you described. My car battery also shows the same weak starting but overcharging pattern. Planning to take it to the shop tomorrow based on your detailed explanation. Before I go, would you mind sharing how much the full repair ended up costing? Also curious if youve had any recurring issues since getting it fixed?

After the repairs were completed, the car has been running perfectly with zero circuit protection warnings or electrical issues. The overvoltage problem was completely resolved by replacing the failing battery, which turned out to be the root cause. The total repair cost came to 290 Euro, which covered the new AGM battery installation and diagnostic testing. This was actually less expensive than expected since the alternator ended up being fine despite the high voltage readings initially suggesting otherwise. The weak starting and electrical glitches have all disappeared. The car battery now maintains proper voltage levels both during starting and while running. Looking back, catching this early likely prevented more extensive damage to the electrical system that could have resulted from continued voltage fluctuations. Just make sure your shop does a thorough check of the charging system to confirm whether your case also only requires a battery replacement or if there are other components affected by the prolonged overvoltage condition.

Finally got the car back from the shop today. The mechanic confirmed it was indeed the alternator causing all those electrical gremlins and overvoltage issues. The total repair came to 1250 Euro including parts and labor. They replaced both the alternator and battery since the old battery was damaged from the constant power surges. The diagnostic testing showed the voltage regulator in the alternator had completely failed, pushing nearly 16V through the system at times. No wonder all the electronics were going crazy. The mechanic explained the high voltage was triggering various circuit protection features, which explained all those unusual system failures. After the repair, the car starts perfectly and all electrical issues have disappeared. The voltage readings are now steady at normal levels. Glad I caught this before it could damage more expensive components. Really appreciate the helpful advice that pointed me in the right direction for proper diagnosis.