Audi S5 Dead After Mechanic Visit, Starter Issue

Had a similar situation with an Audi S4 3.0TFSI 2012. The symptoms matched exactly, no response from the starter solenoid despite a good battery. The root cause was a damaged wiring harness near the starter motor that got pinched during other maintenance work. The voltage drop was significant enough to prevent proper current flow to the starter solenoid and relay switch. After thorough diagnosis, found multiple circuit breaks in the main starting circuit. The wiring harness had to be replaced along with the starter relay. The battery terminals were also cleaned and tightened as a preventive measure. This is a serious issue that requires proper diagnostic equipment and expertise. Taking it back to the original shop is advisable since they should warranty their work if the damage occurred during their service. Make sure they check: Complete starter circuit, Wiring harness condition around the work area, All relay switches in the starting system, Battery terminal connections, Ground straps The problem is likely mechanical damage to electrical components rather than a unusual failure, considering the timing after service work.

Thanks for sharing your experience. Your case sounds exactly like what I am dealing with. My car also shows no starter solenoid response even though the battery checks out fine. I am planning to take it back to the original shop tomorrow. Do you remember roughly how much the wiring harness and starter relay replacement cost in your case? Also wondering if you had any related electrical issues pop up after the repair was done?

Thanks for asking about the repair costs. I actually took the car back and it turned out to be less severe than initially thought. The main issue was a Terminal 15 ignition positive interruption that occurred during their previous work. The power supply was restored by fixing a loose cable connection in the circuit, which was much simpler than replacing the entire wiring harness as first suspected. The total repair came to 95 Euro, significantly less than a full wiring harness replacement would have cost. The good news is I have not experienced any electrical issues since the repair was completed. The car won't start problems disappeared completely once they corrected the faulty connection. The starter solenoid now responds perfectly every time. A proper diagnosis really made the difference, what seemed like a potentially major wiring harness issue turned out to be a straightforward circuit break that was quickly resolved. This kind of electrical problem is often related to disturbed connections during other maintenance work.

I took the car back to the original shop today and got some good news. The mechanic found that during the previous service they had accidentally disturbed the ignition switch wiring while working on something else. The starter solenoid wasnt getting proper voltage due to a loose connection in the circuit break. They fixed it under warranty since it was their mistake. Total cost was 0 Euro and the car starts perfectly now. The diagnostic showed no other wiring harness issues. Really glad I didnt jump to conclusions about needing major repairs. A proper inspection revealed it was just a simple connection problem. The shop was professional about taking responsibility and getting it sorted quickly. Thanks for the helpful advice. Sometimes what seems like a serious electrical problem can have a straightforward fix if you get it properly diagnosed.