Bmw E34 and E32 have a funny tendency to loose the heat in
the middle of winter... If this happens to you time to check
the heater valve.
Heater only works when drivers dial is all the way
to the right (Max. setting) Other settings only produce unheated
air from vents.
Heater valves stuck.
1. Open hood
2. Remove plastic cover to heater valves (located next to
fuse box on firewall)
3. Loosen all six screws on solenoid valve.
4. Tap on both solenoid valves with hammer while an assistant
turns the drivers side temperature dial back and forth.
5. You should be able to hear the solenoid clicking now.
6. Tighten all six screws and replace plastic cover.
7. If this doesnt work you may need to remove and clean
the valves or perhaps replace them.
8. If this doesn't work, change the heater valve
and the auxiliary pump. This is an easy task, you need to
remove the 4 bolts on top of the heater valve, disconnect
the wires and then pull the valve out. You don't need to remove
the auxiliary pump as they will be both pulled out together.
Use needle noise vice grips to pinch the hoses if you don't
want to loose all your coolant. This is a tight spot to remove
the valve but it will come out.