Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

Based on the green/white powder like debris, I'm now 100% convinced that the coolant was leaking from this fitting.
The photo was taken after I cleaned it but there were markings on the side of the blower motor fan case as well as on the battery top surface.

Not sure how it can happen as the coolant hose was not replaced in the past so possibly quality control issue of the cooling hose???
I already saw several example of poor appearance of new cooling hoses so not surprised.






The water valve.
Very simple mechanism and it doesn't make big difference in coolant flow (that controls the air temperature at the heater core) once it is nearly full open.
The first two photos are when it is at 100% open and the latter ones are about 97% open.

However, you will notice big increase in air temperature coming out of the air vent when you move the CCU setting from 31degC to 32degC.
This is because when it is set at 32degC, CCU will force the A/C compressor to switch itself off and blow the air at max speed.
The water valve is at the same position or nearly the same between 31 and 32degC setting so the biggest effect is by the A/C compressor being On or Off.





All of the hoses were replaced at the front compartment.




Same for the ones at the centre floor channel.