loss of airflow on heat setting 4cyl

[Sleeper6]

Hoping someone might be able to point me in the right direction before I dissassemble my dash. On the fiances car the heat setting results in a giant drop in airflow from the vents (on a 1-10 scale about a 3) even on high fan speed, however on cold mix it blows 10/10 for fan speed. Its on the 4cyl auto car and is a bit troubling, as looking in the manual it requires removal of the dash to get at the mix assembly. Checked the lever movement on the sides and it moves fully. Anyone have any ideas as all I can think of is a blockage in the vents but no odd smells so I am kinda confused.

Thanks!

[Sleeper6]

Bump anyone have any ideas? No heat at all except when you first select it, flipping through the manual I dont see any signs of a heater valve does this mean on the b6 hot coolant is constantly going through the heater core and secondly would a bad thermostat cause this?

[Ryan]

Usually - A s--- ton of dog food placed in the ducting by rodents.