VW Lupo Heater Core Failure Causing Low Heat Output

Had a similar heating issue with my VW Polo 2007 TDI. The car heating started working inconsistently, especially during idle. After inspection, the automotive valve controlling coolant flow to the heater core was diagnosed as faulty due to a damaged electrical connector. The engine coolant was flowing correctly, but the electronic signal wasnt reaching the valve actuator. The main issue was actually a corroded wiring connection at the valve plug, not the valve itself. This is a common failure point in VAG cars of this generation. The repair involved cleaning the connector pins, replacing the damaged wiring section, and testing the valve operation. No coolant leak was found, which kept the job straightforward. The car heating returned to normal immediately after fixing the connection. This is usually less severe than a complete valve failure or heater core replacement. Your quoted valve replacement might be unnecessary if its just a connection issue like mine was. Recommend getting the wiring connections checked first before agreeing to full valve replacement.

Thanks for sharing your experience. Your electrical fix sounds like it could be relevant to my situation too, since I have similar symptoms with the heating not working properly. The cooling system seems fine otherwise, with no signs of engine overheating. Would you mind sharing how much the wiring repair ended up costing you? Also curious if you had any other heating issues pop up since getting it fixed? Our cars are from around the same era, so it would be helpful to know what to expect long-term with these car valve problems.

The wiring repair was definitely the right solution and ended up costing 95€ total. After fixing the cable connection to the car valve, the heating system has worked flawlessly for over a year now. No engine overheating or other cooling system problems have occurred since. This repair made much more sense than replacing the entire valve unit. The symptoms were identical to what you describe, inconsistent heating without any actual coolant leak or other issues. The mechanic found the faulty connection during a diagnostic check, and fixing it restored proper function to the heating controls. The 450€ quote you received for a full valve replacement seems excessive when the actual issue might be much simpler. Would strongly suggest having a technician check the wiring connections first, as these electrical issues are quite common in VAG models from that period.

Just got back from the mechanic and wanted to update everyone. After reading the responses here, I asked them to specifically check the wiring connections before replacing any parts. Turns out the automotive valve was working fine, it was exactly the same electrical connection problem mentioned here. The mechanic found corrosion on the connector pins leading to the car valve, causing intermittent heating issues. They cleaned the connections and replaced a small section of damaged wiring. The total repair came to 120€, which saved me over 300€ compared to the original valve replacement quote. The heater core is now working perfectly again, with strong heat output at all engine speeds. No coolant leak or other issues were found during the inspection. Really glad I got that second opinion here before authorizing the more expensive repair. Definitely worth having electrical connections checked first when dealing with heating problems in these older VW models. The whole repair took under two hours and solved the problem completely.