Cold outside, no heat inside

[hans3]

Drove my 2800CS in cold temps for first time. At idle standing still there's sufficient heat coming from the vents. However, at 60+ MPH the vent air becomes lukewarm. Fresh air flap works correctly by switching fresh air completely on / off. Lower "mixture" flap by footwell vents can be seen opening and closing. I cannot observe the upper mixture flap without first removing the blower motor (not too difficult). Coolant hoses in /out of heater core become hot, but not quite as hot as other radiator hoses.

Can this symptom result from any other system air leak, besides an upper mixture flap not closing completely? As an experiment I placed towels on either side of the fresh air intakes to the blower assembly. This allowed air vent output to become acceptably warm (but not super hot) at 60+MPH.

Thanks! -H

 

[2800csm5]

No Heat

What temp. thermostat are you using, should be 80c in the winter.
Is your temp. gauge staying slightly above half at 60 MPH?

 

[hans3]

Thanks for the response. No, my temp gauge is definitely below 1/2, perhaps as low as 1/3 along the scale. I'm running a 75C thermostat; I'm surprised 5C would make that kind of difference at 45F outside temps. I considered this a causal factor until I masked the blower intake with towels--and generated heat.

 

[2800csm5]

Try turning up the heat in your home 5 degrees c and see how much
hotter it gets. Check the seal around your steering shaft ,You could have
cold air leaking through there.