every few seconds my 6100 makes a clicking or buzzing noise. It is very short but happens about every 4 or 5 seconds. This unit is new and has the newer style impeller. It is currently on a tunze bracket. The pump is on a single controller, i unhooked this and ran it without, still made the noise, i have held it in my hand in case the movment of the pump was causing this but it still makes the noise in my hand(the pump also seems to jump or move a little when this noise occurs). thanks Casey