Engine and Heater/blower

[andy-xr]

Trying to work this one out, wondering if it's silted up heater matrix or something else.

Car gets warm and blows reasonably hot air. The quicker I go, the hotter the air. There's no sign of a missing thermostat, as in, it's not taking overly long to warm up and I've checked the pipework which seems to indicate everything is working as it should be.

I've had it where the quicker you go, the colder the air that comes through the vents, but never the other way around. Any clues?

[Astra Dan]

Broken water pump impeller? Very common in modern ones made of plastic.