Fresh air vent?

[nikojo]

My M998 truck has OEM AC system from more recent truck installed which includes heat.

The heat blows well including on the defrost setting on the windscreen through the new plenum.

But when the truck is traveling at speed I can feel very cold air getting through the original vents right next to the windscreen.

How is this possible? Where is that cold air coming from?

Is there some outside air intake tied into the original defrost vents???

 

[nikojo]

Bump

 

[SmartDrug]

Is the fresh air intake on the right hand side of the tub open or closed?

 

[nikojo]

Closed. Assuming thats the round screen that turns to close.

But that isn't connected to the vents/plenum along the windshield that's built into the dash.

 

[SmartDrug]

Mine is, but I have an A2 truck.