Originally Posted by Justohigh
2007 335i E92
Today while driving, I noticed that my heater fan was acting up. As I speed up or slow down the heater fan would slow down and not blow as hard, then all of a sudden start up blowing normally again. This would also happen on some slight bumps in the road also. I also noticed that when I turn the fan setting to the 4th block that is the highest the fan will go. If i turn it up higher, the fan does not blow any harder.
Has anyone ran into this problem or have an idea of what is wrong? I have the JB4 USB running through the fire wall, and was wondering would that cord ever get into the way of the heater fan?
After driving around awhile I noticed that this would happen when I slow down to a stop when the rpm would reach close to idle. The fan would slow down or stutter then speed right back up to normal. Even when I sit in park and rev it up, when the rpm's drop to idle the fan slows down then goes back to normal. Doesn't happen if I'm anywhere above idle. Now I'm really stumped on what this could be?
Check this page out.. Pretty helpful and talks about the example you describe.