Cabin heater matrix

[ColinLaughton]

Hi,

I'm going insane..

Never had good heat from my 2007 1.3 Yaris. I have down the following:

Replaced water pump
Replaced thermostat and checked working at temp
Back and forward flushed matrix and observed no dirt coming out, and smooth fast flow exiting matrix in both directions.

When car is at temp, some heat comes into the cabin.... But mostly from left side vents but not right. This heat is poor but there.

The matrix pipes are RED hot going in and slightly less red Hot going back to engine.

The actual matrix when checked on the side of the pipes is HOT

No signs of coolant leaks in cabin or in engine bay.

HELP!!!! 😭

MANY THANKS!