Audi A5 Turn Signal Faults Point to Electrical Glitch

I had a very similar electrical fault on my Audi A4 2014, and I have some experience working with automotive lighting systems. The symptoms were nearly identical, intermittent turn signal operation and persistent bulb replacement warnings. Initially thought it was a simple bulb replacement job, but the workshop diagnosed it as a faulty connection in the wiring harness near the front driver side lamp assembly. The issue was triggered by a corroded plug connection that was causing poor contact, leading to those confusing flasher relay signals. The repair involved cleaning the connector terminals and replacing a damaged section of the wiring harness. Total cost was 95 Euro for parts and labor. The interesting part was that the turn signal would work fine sometimes, making it tricky to diagnose. The workshop used specialized diagnostic equipment to trace the electrical fault to the exact connection point. Before we go further into specifics, could you share: Have you noticed any moisture in the headlight assembly? Does the issue occur more frequently when driving over bumps? Are there any other electrical issues like dashboard warnings? Have you recently had any front-end work done? This information would help determine if your A5 is experiencing the same connection issue I encountered.

Thanks for sharing your experience. At 162817 KM after my last service, I also suspected a basic lamp replacement would fix it. Got it checked and discovered moisture had corroded the turn indicator connector, causing similar intermittent faults. Checking the electrical fault codes showed multiple errors related to the signal lamp circuit. The wiring harness near the connector was also damaged. Turned out more complex than initially thought, definitely beyond a simple automotive lighting fix.

The corroded connector issue seems to be a common problem in our model range. After my initial repair, I discovered that water ingress around the broken lens seal was the root cause of my electrical fault. The moisture problem tends to worsen in these cars as they age, especially around the 150000-170000 KM mark. The workshop explained that the indicator light failures often start intermittently because corrosion gradually builds up in the connector housing. My flasher relay also showed similar symptoms before the complete repair. The multiple error codes you mentioned match exactly what I experienced, it is typical when the connection deteriorates to the point where the car computer cant get reliable signals from the lighting system. The total repair on my car included: New wiring harness section: 45 Euro, Connector assembly: 35 Euro, Replacement lens seal: 25 Euro, Labor: 90 Euro Make sure they properly seal the housing after repair to prevent future moisture issues. Since fixing mine properly with new seals, the electrical system has been fault-free for over 30000 KM.

Thanks everyone for the detailed responses. Really helpful to know about the water ingress being a common issue. Just got my A5 back from the workshop today, total bill came to 180 Euro including a new wiring harness and connector replacement. They found the exact same problem with moisture corroding the turn indicator connections. The broken lens seal was letting water seep in gradually over time, creating those electrical fault codes. The workshop also replaced all the seals and gaskets around the housing to prevent future issues. They mentioned these automotive lighting problems are pretty common once the cars get higher mileage. The flasher relay is now working perfectly and all the error codes have cleared from the system. No more intermittent signal lamp warnings either. Good to know I wasnt alone with this issue. Will definitely keep an eye on any signs of moisture around the headlight assemblies in the future. Thanks again for helping diagnose the problem!