Hi my system has started doing much the same thing for a while, then stopped, did the same thing a few weeks later at 5 in the morning. Then today, the fan motor stopped working. Fault appears to be with the electrical fan motor, which is now died. They do need cleaning as they build up dirt and fluff etc, but it now a replacement unit for me.
Will look to see if I can get the old fan motor repaired, but needs must so a replacment is required now.
I have my system serviced every year and they do build up some crap inside.
Pip
December 2009