Lack of heat in heater mode

[Louis Ducap <louisd@xxxxxxx>]

Bmw 735i 1988 E32

Outside air temperature in the range +15F to -25F.

Initially, when car is not moving, with defrost or heat selection, I get
about 140F out of any outlet, then for no reason and after about 5 minutes
of use, temperature drops to 90F at the outlets.

After driving the car for 2 to 3 minutes, the outlets are getting cold. The
system has been flushed and refilled with coolant. The two heater valves
have been cleaned and reseated. The electrical connectors at these valves
are cleaned. The two inlet hoses going to the heater core and outlet hose
are hot and the core has been cleaned.

The temperature gauge is in the normal range (mid position) during the
events.It is therefore NOT the thermostat...

The different selections at the heater controls seem to be working like the
book says.

It feels like there is a cold air intake trap which is fully opened or
partially opened and letting too much outside air mix with the heated air at
the heater core.

Can somebody help me with this. I'm baffled!.....and frozen. It's reaaly
cold with these winter blizzards.

Louis

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