Mercedes Citan weak heating issue

I had something similar with my Citan. Weak heat and a water valve error. Check the engine coolant level first. A leak can cause this. Also, check the heater core hoses for blockages or kinks. If those are okay, then replace the water valve.

Can you tell me more about checking the heater core hoses? What should I look for with a valve blockage, and where are they on the Citan?

On my Citan, the heater core hoses are in the engine compartment, going to the firewall. Feel them. If one hose is much hotter than the other, that could mean a valve blockage. But with the error code, it probably is the water valve. I'd go to a shop to be sure.

I understand. Thanks for the explanation and advice. I'll have a shop check the water valve and do the repairs. I'll also have them check the coolant level and heater core hoses like you said. The repair was the water valve, costing 95€ as expected.