Heater problems

[jacksonjack]

Has anyone ever experienced a problem like this? I start the chero and let it warm up. the heater works fine putting out nice toasty heat. about 15 minutes into driving the air coming into the cab starts to get cooler and cooler until no heat is coming out. Temp gage reads normal. I have back flushed the heater core. has a new radiator. any ideas?

[woodybeone]

Is there a hole in the heater duct allowing cool air to be forced in when driving? Other test is to stop and grab each hose at the heater core and see if they are both hot/warm. What temp. thermostat is in it? May want to change it.

[Jlamb]

When you get this cold air are the heater hoses about the same tempature, and if they are, are they hot?