No, there's only one.
See this thread:
http://www.bimmer.info/forum/showthread.php?t=17981
Or this one:
http://www.bimmer.info/forum/showthread.php?t=17970
Or search for "heater core". It's a common problem. Here're some instructions for fixing it:
http://www.homeofsbc.com/Fixes/Heater/heater.htm
The consensus seems to be that it is a reasonable DIY job, but VERY time consuming -- 8-10 hours.