Heater blowing luke warm not very warm?

ArsenalFC

Got this problem in a nissan micra. The fan is working fine as there is a good blast of air when turning fan on full, but the heater is just luke warm even if engine temperature is at warm (midpoint).

Anyone know what the problem might be. Need to get it sorted for the winter as it will take ages to clear steamy windscreen and keep the cabin warm.

Tight_Git_3

I had a similar problem in an old Nissan Sunny. The heater matrix - like a smaller version of the radiator had got blocked up over the years.
I had to drain the coolant, and then attached a hose pipe to just about every pipe I could disconnect and gave the whole thing a good blasting out with clean water.
Filled it back up with antifreeze mix and problem sorted.