RS3 Heating Failure: Faulty Water Valve Symptoms & Fix

Based on my experience with a 2019 RS5 that had similar car heating issues, I can share some relevant insights as someone with moderate expertise in Audi repairs. The symptoms you describe match what I encountered, minimal heat output and error codes related to the cooling system. In my case, the water valve was functioning correctly, but the issue stemmed from a faulty cable connection to the heating control module. After diagnosing engine overheating concerns, my mechanic found that the valve blockage signals weren't reaching the control unit due to damaged wiring. The repair involved: Complete diagnostic scan, Testing the car valve functionality, Replacing damaged wiring and connections, System reset and testing Total cost was 95 Euro for parts and labor, which seems reasonable for this type of repair. Before suggesting specific solutions, it would help to know: Which error codes are you getting? Does the problem occur when the engine is cold or warm? Have you noticed any changes in engine temperature? Are there any unusual sounds from the heating system? This information would help determine if your issue matches what I experienced or if you might be dealing with a different heating system problem.

Last service was at 90000 KM, and Im adding more details about my heating issue. The error codes are P0597 and P0599. The issue occurs mainly when the engine is cold, and yes, I notice the temperature gauge shows slightly higher readings than normal. No unusual sounds from the heater core area, but there is a slight sweet smell which might indicate a coolant leak somewhere in the system. The heating works a bit better after driving for about 30 minutes, but never reaches proper temperature. After checking closer, I also noticed small coolant spots under the car. Could this indicate a more serious issue with the heater core rather than just the automotive valve?

Your coolant leak symptoms are definitely concerning and match what I experienced before my repair turned into a bigger issue. Initially, I also thought it was just the automotive valve, but those coolant spots and the sweet smell are classic signs of a heater core problem, I learned this the hard way with my RS5. Those error codes (P0597 and P0599) relate to thermostat heater control circuit issues, but in my case, they were secondary symptoms. The primary issue was indeed a failing heater core, which explained the coolant leak and poor heating performance. When my mechanic investigated, they found: Coolant was leaking from the heater core joints, The valve blockage was actually caused by corroded coolant passages, Engine overheating occurred because of low coolant level The repair involved: Heater core replacement, Complete system flush, New coolant, Thermostat replacement as preventive measure Total repair cost was 750 Euro, significantly more than just a valve replacement, but it solved all issues including the error codes and prevented potential engine damage. My advice is to address this quickly, continuing to drive with a leaking heater core can lead to more serious engine overheating problems and potentially damage other components in the heating system.

I appreciate all the detailed responses and information shared. The symptoms you described with your RS5 sound very similar to what Im experiencing. Looking at those repair costs, 750 Euro is steep but makes sense given the comprehensive work needed. After hearing about your experience with the heater core issues, Im going to book the car in next week for a proper diagnosis. The coolant spots and sweet smell have me worried about potential engine overheating if I keep driving it like this. Better to fix the entire cooling system properly than risk more damage. One last question before I schedule the repair, did you notice any improvement in overall engine temperature management after getting the heater core replaced? Im wondering if fixing this might also help with the slightly elevated temperature readings Im seeing on the gauge.