S5 AC System Dead: Quick Diagnosis & Cost Guide

I had a similar AC efficiency problem with my 2014 Audi S4 last summer. Having some experience with AC maintenance issues, I initially thought it might be just low refrigerant, but it turned out to be more complex. After checking multiple components, my mechanic found defective valves in the AC system. The blower motor was working fine, but the temperature control system wasnt responding due to these faulty valves. The AC relay was tested and showed no issues. The complete repair, including parts and labor, cost me 1000 Euro. The work involved: Full system diagnosis, Replacement of faulty valves, Refrigerant recharge, System pressure testing To better assist with your S5 issue, could you share: Any unusual sounds when trying to activate the AC? Does the blower motor run at all when you turn on the fan? Have you noticed any moisture or wet spots under the car? Any warning lights on the dashboard? These details would help determine if youre facing the same issue I had or if its something different with your AC system components.

Last service was at 116593 KM. Thanks for the thorough response, but my symptoms are slightly different. I dont hear any sounds at all when pressing the AC button. The blower motor seems completely dead, no air circulation whatsoever. I had no warning lights appear on the dash, and havent noticed any moisture underneath. Based on your experience, this sounds more like an electrical issue rather than the valve problems you encountered. Going to schedule some AC diagnostics to check the relay and electrical connections first before diving into the more complex components.

Thanks for those additional details, definitely sounds different from my valve problems. Since your blower isnt responding at all, this points strongly toward an electrical component failure in the AC system. From my experience with these Audi AC systems, when theres zero response from both the AC and blower, the pressure switch is often the culprit. The pressure switch acts as a safety feature, shutting down the system if pressure levels arent correct. After my valve repair, I actually faced a similar complete shutdown about 6 months later. The issue turned out to be: Failed pressure switch (200 Euro part), Blown fuse connected to the blower circuit, Faulty electrical connection at the temperature control module The repair was much cheaper than my previous valve issue, coming in at 350 Euro total including labor. The AC efficiency returned to normal immediately after fixing these electrical components. Before you head to the shop, you might want to: Check the fuse box for any blown AC-related fuses, Listen for any clicking sound from the relay when pressing the AC button, Monitor if theres any AC noise at all, even faint, when starting the car Let us know what the diagnostics reveal, electrical issues are usually more straightforward to fix than mechanical AC problems.

Based on the exchange, I can understand this seems to be an electrical rather than mechanical issue. The advice about checking the pressure switch and AC system fuses makes sense for my situation, especially since there's zero response from the controls. Will definitely start with checking the fuses and have the pressure switch inspected. The complete silence when trying to activate the AC does match with what was described about electrical failures. This should hopefully be a simpler fix than a full valve replacement. Planning to have it checked next week and will focus the diagnosis on the electrical components first. The repair cost estimate of around 350 Euro for similar electrical issues is much more reasonable than what I was fearing. Good to know the AC efficiency can be restored without major mechanical work if it is indeed just the pressure switch or related electrical components. Thanks again for sharing the repair details. The specific troubleshooting steps will help me better communicate the issue to my mechanic.