e34 Lack of Heat

[Rick Gutierrez <rickg@xxxxxxxxxxxxx>]

I first started having problems with the heat of my 1994 525i (NON-CLIMATE CONTROL) this past November. I discovered the diaphragms of the heater valve were disintegrated. Oh well, its cold here so I removed the two metal plungers and reinstalled the heater valve on the car, figuring Id have max water flow at all times which would be a good thing.

That failed to produce an increase in interior heat. I then changed the thermostat with a 92 degree C (197 degree F) unit from the BMW dealer. According to the dash water temperature gauge, the old thermostat as well as the new one ran at about the 12 oclock position. The heat in the car was adequate for temps above 20 degrees F. In fact using a certified digital thermometer, with an outside ambient of 25 degrees F and blower speed on #2 the vent discharge was 139 degrees F. 

This week the temp has turned to single digits and last night it dropped to zero. It was somewhat of a chilly ride this morning, as Id have to guess the discharge air temp from the vents was about 120 degrees F. The blower motor was on #4 for my 35 mile commute to work and the system was barely able to keep frost off the inside of the windshield. 

I cant believe the design of the center console discharge vent, there is some very cold air entering the system. Even though I have the vent shut-off so as not to blow cold air to the back seats, that air is still probably "leaking" into the cabin. I find no explanation of this in the owners manual or the Bentley manual.

Speaking of the Bentley manual, I was reading over the wiring diagram found on pages EWD-131 thru 133. How much of this system is on my car? Im trying to sort out other possibilities of what else could be wrong with this car, or is this the best the heat will ever get? What symptoms would I experience for defective heater core sensors? How do the air distribution motors work and what would I experience if flaps did not distribute air properly? How would I diagnose a defective heater core? The Bentley manual lacks a theory of operation of the system or sub-components.

Im a proud BMW driver but when my girlfriends 1991 Honda Prelude pumps out better heat than my 525i, thats downright embarrassing.

Hope someone can help!

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