Poor Defroster Air Flow - any experience

[Dave Underwood]

Has anyone had poor air flow out of the defroster vents on a later G model.

The problem is one of what seems to be low levels of air flow out of the defroster vents, even when we set the controls and close all the other vents on the floor. There always seems to be a disportionate amount of air coming out of the floor vent on the right of the console as well as those on the floor that you can not shut off.

We have looked at the diverter valve behind the right pedal and see one flap valve which controls air to the thermostat and thus the cycling of the heater and another that is supposed to control warm air to the defrost. The defrost valve appears to operate backwards to expectations, but does open and close the outlet that leads to the scatt tube and then upwards to the top of the panel.

It would appear that when the defrost lever is in the down and on position, that its valve is actually partially closed. When you put the control in the upper position showing defroster off, the valve is actually fully open. It would seem to be backwards although everything is rigged per the diagram in the service manual.

Another question is, am I being unrealistic expecting a strong flow through the defroster vents? Please, no comments about Cessna engineering and Design.

Has anyone taken this area apart or looked closely at how it works and how the air is supposd to flow?

Regards - Dave