Engine Overheating and Low Car Heating Output

I understand you are experiencing issues with your Mercedes X Klasse. I encountered a similar problem with my X Klasse some time ago. The inadequate heating and the error code pointing to the water valve suggest a disruption in the cooling system's ability to regulate temperature effectively. Think of it like this: your engine's cooling system is like a circulatory system and the valve is like a critical artery. If that artery is blocked, circulation is reduced. Have you checked the coolant level, as low coolant can also affect heating performance? Also I am curious, are you experiencing complete failure of the heater, or does it function intermittently?

The coolant level is fine, I checked it. The car heating is not completely failing, it's more like it's weak. It does get a little warmer when the engine's been running for a long time, but never properly hot. Was your issue exactly the same, weak heating and the same error code?

Yes, the symptoms you describe align closely with the issue I experienced. Given that the coolant level is adequate and the heating remains consistently weak despite engine temperature, the water valve is the prime suspect. While it could indeed be a cable or connection issue, a partially blocked or malfunctioning valve is also plausible. To be certain I suggest visiting a workshop to properly diagnose the valve. Replacing the valve should resolve your issue.

Thanks for confirming. I suspected as much. I'll book it in at the workshop and get the water valve checked and replaced. Hopefully, that'll sort it out. I'll report back once it's done.