Arteon Heater Failure: Water Valve vs Core Issue Fix

As someone with moderate experience working on VWs, I had a similar issue with a 2019 Passat last winter. The symptoms match exactly what you described, minimal heat output and a warning light. The water valve was indeed the culprit in my case. During diagnosis, the shop found a faulty connection at the valve control unit that was preventing proper coolant flow through the heating circuit. The cooling system itself was working normally, but the valve blockage meant barely any hot engine coolant was reaching the heater core. Total repair cost was 95€ including diagnostics and fixing the cable connection. They tested the valve operation before and after to confirm it was now functioning correctly. Much cheaper than replacing the entire heater core, which they initially suspected might be needed. To help provide more specific advice, could you share: Your Arteon build year, Current mileage, Exact error code showing, When the heating issue started, Whether the heat output varies with engine RPM This would help determine if your case matches what I experienced or might point to a different component in the heating system.

Latest service was just 2 weeks ago at 100350km. The automotive valve diagnosis you mention matches my symptoms perfectly. The error code is P0597 and heat output stays minimal regardless of RPM. When they serviced it, the cooling system pressure test was normal, which seems to confirm the main cooling circuit works fine. So the water valve control being the likely culprit makes a lot of sense. I will have them focus checking that valve blockage point first rather than jumping straight to heater core replacement. Hoping for a similarly straightforward fix with the car valve connection rather than a major repair. Thanks for sharing those diagnostic details, really helpful for my upcoming shop visit.

Thanks for the additional details, and the P0597 code definitely confirms what I suspected initially about the water valve control issue. After getting my Passat fixed, I learned these valve problems are relatively common around the 100000km mark in our generation of VW models. The fact your cooling system passed the pressure test is another good indicator. When I had my valve control unit fixed, the shop mentioned they see this failure pattern regularly, the electronics or wiring at the valve control go bad while the rest of the cooling system stays perfectly fine. One thing I noticed after my repair, the heat output improvement was immediate and dramatic. The valve started routing hot coolant properly right away. Keep an eye out for that when they fix yours. If the heat doesnt return to full strength immediately after the repair, it might indicate something else in the heating circuit needs attention. Since your symptoms and mileage match my experience so closely, I am even more confident the engine overheating protection system is just doing its job by limiting flow through a faulty valve control. Let us know what the shop finds when you get it checked.

Good news to share, got my Arteon back from the shop today. The coolant leak diagnosis confirmed exactly what you suggested about the water valve control issue. They found a failed connection at the valve unit that was preventing proper coolant flow to the heater core. Just like you predicted, once they repaired the automotive valve connection, heat output returned to full strength immediately. Total cost was 115€ for diagnostics and the valve repair. Much better than replacing the entire heater core which they originally thought might be needed. Really appreciate the detailed insight about the valve control problems being common at this mileage. Saved me both time and money by having them check that specific issue first. The car valve repair was quick and the heating now works perfectly again at all settings. Will definitely keep an eye on the heating system performance over the next few weeks, but so far the fix seems solid. Thanks again for helping point them in the right direction with the diagnosis.