Talisman weak heating water valve fault

Weak heating and a water valve error definitely point to a problem in the cooling system's control of coolant flow to the heater core. The heater core is essentially a small radiator inside your dashboard that hot coolant flows through to heat the air. A defective water valve could prevent hot coolant from reaching the heater core, resulting in the low heating output. Before jumping to conclusions, have you checked the coolant level? Is the engine overheating?

Coolant level is fine, and the engine temp is normal. If the engine isn't overheating, does that rule out a valve blockage?

Not necessarily. A partial blockage, or a valve that isn't opening fully, could still restrict flow to the heater core specifically, without causing overall engine overheating. The fact that you have an error code pointing to the water valve itself makes it more likely the valve is the issue, or as you suspected, the electrical connector to it. Given the stored error and your symptoms, I'd advise a workshop visit to diagnose the valve and its wiring properly. The repair shouldn't be too expensive.

Thanks for the advice. I took it to the shop, and you were spot on. It was a faulty connection to the water valve, just like I suspected. New connector and all sorted for 95€! Much appreciated!