Vauxhall Vectra Heater Output Low

I had a similar problem with my 2012 Peugeot 308. The heater blew cold, and it was a faulty thermostat. The error code pointed to a coolant issue, but we thought the heater core was blocked. Have you checked for coolant leaks? What does the error memory say? Check the valve for blockages or if it opens and closes right.

Thanks! I haven't seen any coolant leaks, but I'll check. I don't know the exact error code, but my mechanic said something about the water valve circuit being open. How did you figure out the thermostat on your Peugeot? Was the error code the same?

The error code was different. But the symptoms were similar: poor heating and a coolant error. My mechanic tested the cooling system and saw the thermostat wasn't opening right, so the engine ran cooler. Since your mechanic suspects the water valve and the error code mentions an open circuit, I'd trust him. Get it diagnosed and fixed at a workshop before it gets worse.

Thanks for sharing! It was the water valve. The repair was 95€, parts and labor. Hopefully, that fixes it.