Audi Q8's Terminal 30 Power Issues Stalling Startups

As someone with some car repair experience, I had a very similar electrical fault on my 2018 Audi Q7. The symptoms matched exactly what you describe, weak cranking and inconsistent starting behavior. The issue turned out to be a heavily discharged battery that was causing problems with the starter motor and overall electrical system. After thorough testing, the workshop discovered the battery was not holding charge properly and the charging system was working overtime to compensate. The diagnosis process involved: 1. Full electrical system scan 2. Testing the battery capacity 3. Checking the starter motor connections 4. Inspecting the wiring harness for potential damage 5. Testing the ignition switch functionality The complete repair cost me 290 Euro, including a new battery and system diagnostics. The fix resolved all starting issues completely. Before suggesting specific solutions, could you provide: Current battery age, Any warning lights on the dashboard, Whether you notice dimming lights when using electrical accessories, If the car sits unused for extended periods, Recent changes or repairs to the electrical system This information would help determine if your Q8 is experiencing the same root cause as my case. Its important to have the fuse box connections checked as well, as corrosion there can cause similar symptoms.

Thanks for the detailed input. After checking my maintenance records from the last service at 41894 KM, I discovered several voltage drops had been noted but not addressed. My initial suspicion about the power supply issues seems more likely now. The ignition switch works normally when the battery is freshly charged, but problems return within days. After testing with a multimeter, I measured inconsistent voltage readings at different terminals. The wiring harness appears intact, but there might be hidden electrical faults causing parasitic drain. Will have the workshop perform a full charging system diagnosis and check all terminal connections. Thanks for the troubleshooting steps, they align well with what the manual suggests for power-related starting problems.

Glad my previous advice helped narrow down the issue. Since we both have similar Audi models, I can confirm that voltage drops like youre experiencing often point to a failing charging system rather than just a battery issue. In my case, after the initial battery replacement, we also discovered corroded connections at the starter motor that were causing resistance in the circuit. The inconsistent multimeter readings you mentioned match what I experienced, it took the workshop several diagnostic steps to trace it to a combination of issues within the charging system. They found that while the alternator was functioning, the voltage regulator wasnt maintaining stable output. The short circuit testing revealed multiple small draws that added up to significant battery drain. The wiring harness connection points need special attention on these models, as their positioning makes them susceptible to moisture damage. Since your symptoms persist after charging, Id specifically request checking: 1. Alternator output stability 2. Voltage regulator performance 3. Starter motor solenoid connections 4. Ground strap integrity The complete repair might cost more than my initial 290 Euro case if multiple components need attention. Make sure they do a full parasitic draw test, its crucial for these models when experiencing recurring power issues.

Thanks everyone for the helpful responses. I scheduled a workshop visit and provided them with all the diagnostic points mentioned. The technician confirmed the voltage drops in my maintenance records match common symptoms of charging system deterioration. The multimeter readings I took showed fluctuations between 11.8V and 12.4V at the power supply terminals, which apparently indicates potential issues beyond just the battery. Given the recurring nature of the problem even after charging, I agree its likely a combination of factors affecting the electrical system. Will have them perform comprehensive testing of the alternator, voltage regulator, and check the fuse box connections thoroughly. Ill ask specifically about parasitic drain testing and examining the starter motor circuits. The workshop quoted around 450 Euro for full diagnosis and potential repairs, seems reasonable considering the complexity of modern vehicle electrical systems. Will update once I get the final diagnosis and repair details. Really appreciate all the technical insights shared here, helped me better understand what to look for and discuss with the technicians.