VW Scirocco Heater Output Issues & Troubleshooting

I had this exact same issue with my 2014 Golf GTI last winter. With some car repair experience, I knew right away it was likely related to the automotive valve system. The symptoms were identical, weak heating performance and fault codes pointing to the cooling system. Initially thought it was valve blockage, but after inspection, the workshop found the cable connection to the heater control valve was loose and partially damaged. The fix was straightforward, they replaced the wiring connection to the car heating control unit and recalibrated the system. Total cost was 95€ including diagnostics. Since the repair, the heating system has worked perfectly, especially during cold starts. Before suggesting specific fixes for your Scirocco, could you share: Current mileage, Exact fault code stored in the system, Whether the heating performance varies with engine RPM, Any unusual sounds from the heating controls, When you last had the cooling system serviced This information would help determine if your issue matches what I experienced or if it might be something different in the cooling system.

Thanks for your response. My Scirocco has 23624km and had its last service 3 months ago. The heating performance stays consistently weak regardless of engine RPM. No unusual sounds coming from the controls. The fault code is P0597, which points to a thermostat heater control circuit issue. During the last service, they checked the engine coolant levels and found them normal, with no visible coolant leak. Speaking of cold starts, the car takes noticeably longer to reach operating temperature lately. I am wondering if this points more toward a faulty water valve rather than just wiring, given that the recent service should have caught any loose connections.

Based on your description and the P0597 code, this actually sounds more serious than my initial wiring issue. While our cars are similar, the symptoms you describe, especially the slower warm-up time, strongly suggest a failing water valve rather than just a wiring problem. After getting my wiring fixed, I encountered a similar issue 6 months later. The engine coolant was circulating incorrectly due to a stuck water valve, causing both poor car heating performance and extended warm-up times. The engine overheating warning never triggered, but the heating efficiency was terrible. The repair involved: Replacing the water valve: 180€, New engine coolant: 45€, System diagnosis: 60€ Total came to 285€, but it completely resolved both the heating issues and normalized the warm-up time. Important to know: delaying the repair could lead to more serious engine cooling problems. Your low mileage suggests this might be a component failure rather than wear and tear. Consider getting the water valve checked soon, especially since your car heating performance stays weak regardless of RPM, that was exactly what happened in my case before the valve completely failed.

Thanks for the detailed responses. After reading through the experiences shared, I think I'll book my Scirocco in for a proper inspection. The consistent heating issues and that P0597 code, combined with the longer warm-up times, really point toward the water valve being the culprit. 285€ for a complete fix including new engine coolant sounds reasonable, especially considering the risk of more serious problems if left unchecked. Better to address it now than wait for potential valve blockage or more severe engine cooling issues down the line. Good to know about checking both the wiring and the valve itself, I'll make sure to mention these specific symptoms to the workshop. Really appreciate the help in narrowing down the problem. Will update once I get it sorted.