Heater question

[Varinn]

My 1990 325i heater (with AC) works great, when set to maximum on the temp dial. Fan speed doesn't matter but obviously more airflow is warmer. When you turn the temp dial down even 1/4", the heat disappears drastically and it blows what seems like full-cold. This makes it a pain in the ass sometimes to regulate temperature in the car as it's either skin burning hot, or cold. Is this normal for an e30 or should I be investigating a heater valve problem maybe? The only thing I've noticed is that the knob turns easily from cold to hot, but when going from hot to cold it feels like it gets stuck at 1/2" from max hot. Once you turn it past that it moves easily again.

Fan speeds work on all settings
Engine temp warms up relatively quickly and always stays a hair under the half way mark once warmed up

[jeffnhiscars]

Random thoughts are: bad heater valve, air in system, partially blocked core. Not sure if the heater core bypass recall can cause this but thats something else to consider

[dnguyen1963]

Check the air flap.

[jlevie]

The heater valve is either open or closed and the valve opens when the temperature dial is turned just a bit from full cold. Temperature control is from adjustment of the air doors. An obstruction in coolant flow through the core or a fault in the air doors are the likely causes in this case.