S4 Electric Fan Issues Lead to Dangerous Overheating

As someone with decent hands-on experience working on Audis, I faced a similar issue with my 2019 Audi S5. The radiator fan symptoms were almost identical, vehicle overheating during idle and slow traffic, but better cooling at higher speeds. After inspection, it turned out the electric fan wasnt activating due to a damaged wiring connection between the fan motor and the control module. The workshop found corroded terminals in the fan motor connector, which prevented proper electrical contact. The repair involved cleaning the connections and replacing the damaged wiring harness section. Total cost was 95 Euro and the repair took about 2 hours. Since then, the electric fan has been working perfectly and no more overheating issues. Before suggesting specific fixes for your S4, could you provide: Current mileage, Any check engine lights, Whether you hear the fan running at all, If the problem started suddenly or developed gradually This information would help determine if your issue matches what I experienced with the fan motor connection or if its potentially a different component in the cooling system.

Thanks for sharing that experience. My S4 has 108938 KM and last service was 2 months ago. No check engine lights are on, but I notice the electric fan only works intermittently. The cooling system worked fine before, but the overheating started gradually over the past 2 weeks. The temperature control gauge now regularly shows higher readings when stopped at lights. Sometimes I hear the fan kick in briefly, but it doesnt stay running like it used to, even when the engine is hot. After reading about your wiring issue, I will have the fan motor connections checked first before considering a full replacement.

Thanks for those details, the symptoms youre describing sound nearly identical to what I experienced with my S5. The intermittent fan operation combined with the gradual onset strongly suggests an electrical issue rather than a complete electric motor failure. When my fan started acting similarly, I initially thought the entire fan assembly needed replacement. However, the root cause was those corroded connections affecting the signal to the fan motor. The fact that your fan occasionally kicks in suggests the motor itself is likely still functional. Since your cooling system performs better at speed and the issue developed gradually, this matches the pattern of deteriorating electrical connections in the fan circuit. The natural airflow at highway speeds masks the problem, but the lack of proper electric fan operation becomes obvious during idle. The fix on my S5s cooling system was straightforward once properly diagnosed. Id recommend having those connection points checked first, particularly the wiring harness near the fan motor where moisture tends to accumulate. This approach could save you from unnecessarily replacing the entire fan assembly. Also worth mentioning, while checking the connections, have them inspect the fan relay. Sometimes the vehicle overheating can be traced to a failing relay rather than the wiring or fan motor itself.

The patterns youre describing match my situation perfectly. I feel more confident now about the likely cause, especially since my fan control issues developed gradually like yours. The correlation between intermittent fan operation and a potential wiring problem makes sense, particularly given how the temperature control works fine at higher speeds. Ill have my mechanic focus first on inspecting the electric motor connections and fan relay before considering more extensive repairs. Its reassuring to know this might be fixable without replacing the entire fan assembly. The fact that my cooling system still functions properly at highway speeds, just like in your case, gives me hope that this is primarily an electrical issue rather than a major component failure. Thanks for suggesting the inspection of the wiring harness near the fan motor. It helps narrow down where to look first, and hopefully the fix will be as straightforward as your S5 repair was. Ill update once I get it checked out, as this could help others who experience similar overheating issues with their Audis.