Weak Cranking S6: Hidden Terminal 30 Power Issues

As someone with some hands-on experience working on Audis, I had a very similar electrical fault on my 2012 Audi S4. The symptoms matched yours exactly, poor cranking despite a new battery. After multiple diagnostic attempts, my workshop found the issue was related to the main power supply connection at the fuse box. There was corrosion building up at a main terminal, causing intermittent voltage drop issues. The complete diagnosis and repair cost me 290 Euro, which included: Full electrical system diagnostic, Cleaning and replacing affected terminals, Testing the circuit breaker functionality, Verifying proper voltage across all relevant connection points Before suggesting specific fixes for your S6, could you share: 1. Any warning lights on the dash? 2. Does the issue happen more after the car sits for several days? 3. Have you noticed any other electrical issues like dim lights or slow power windows? 4. Did you check the battery terminal connections for corrosion? The continuous power supply issues can be tricky to diagnose without proper testing equipment, as the problem could be anywhere in the circuit from the battery to the starter motor. Getting these additional details would help narrow down if youre facing the same underlying issue I encountered.

Had my car serviced last month at 172669 KM and they checked all battery connections and ground points which were clean and properly torqued. No warning lights showing on the dash and electrical systems work normally otherwise. The starting issue seems unusual rather than time-dependent, sometimes it starts perfectly, other times it needs multiple attempts regardless of how long its been sitting. The charging system tests good with 14.2V at idle, and voltage drop readings at the starter motor are within spec. Could there be a failing component in the wiring harness thats causing intermittent connection issues even though everything looks intact? Would appreciate knowing what specific tests were done in your case to pinpoint the location of the loose connection in the fuse box.

Looking at the symptoms you described, the intermittent nature definitely matches what I experienced on my S4. The key difference is that my issue was clearly traced to the fuse box terminals, while yours seems more complex since all connections test good. After your feedback, I suspect the ignition switch might be the culprit in your case. When my shop did the full diagnosis, they performed a voltage drop test across multiple points while attempting to start. They found: Main battery terminal to starter motor: 0.2V drop (normal), Terminal 30 to fuse box: fluctuating readings (this was my issue), Ignition switch circuit: stable readings For your case, Id suggest having them specifically test: 1. Voltage stability at Terminal 30 while cranking 2. Complete circuit testing of the starter motor solenoid 3. Signal testing at the ignition switch during multiple start attempts The charging system reading of 14.2V is good, suggesting the alternator isnt the problem. Since all visible connections are clean and tight, the electrical fault is likely inside a component rather than at a connection point. My repair ended up being straightforward once properly diagnosed, but it sounds like you might be dealing with an internal ignition switch or starter solenoid issue rather than a simple connection problem.

Thanks for that detailed info about the diagnosis steps. Given my clean connections and normal voltage readings, I agree the issue might be more internal than external. The voltage stability test at Terminal 30 while cranking makes a lot of sense as a next diagnostic step. My mechanic actually has access to a digital scope, so I'll ask them to monitor the voltage patterns during multiple start attempts, focusing on both the ignition switch circuit and starter motor signals. Since the charging system and basic power supply circuits test good, an intermittent internal component failure seems the most likely culprit. Will get those specific tests done and report back on what they find. Hopefully pinpointing the exact location of the voltage drop during cranking will lead us to the failing part. Really appreciate you sharing the detailed diagnostic process from your similar case, gives me a clear path forward for troubleshooting this frustrating starting issue.