Heater problem on my BMW 318ti compact

Blower motors with could be stuck. Replace the adjustment switch in your dash.

Did you recently add Freon in your AC system? You might have too much Freon in the system, which caused the AC compressor to recycle more frequent than normal. Or you might not have enough Freon in the system. These BMW's are very AC system are very finicky. Get an AC gauge and check the level (high side & Low side) pressure.

Check the basics first start with water and oil levels make sure they are where they need to be. If that doesn't work try replacing the thermostat

Try here

https://www.carstereocode.com/unlock.php?id=1126

By the blower motor ,there's a resister,replace.

They are so close to the same wiring and mounting and only a couple pounds different in pressure it should work out from my calculations

You might very well have a blocked radiator.Try this.With the car running and standing still,turn on the heater and the interior fan at full.If it takes longer to get hot its the radiator.The heater unit takes a lot of hot air from the cooling system and is a good indictator.this is just a start.There is a few things it might be,but this might narrow it down.Hope this helps

try this link
http://autorepair.about.com/library/firing_orders/bl-fo-5775.htm

Can be low coolant level or water pump problem.
Check the coolant level.
Also alternator (serpentine belt) can be a problem too.
Good Luck