My G646 SC had the same problems as others listed here e.g. water (about half a cup) coming out of the fan vent when the door was opened to empty the dishwasher, and the fan was becoming noisy.
The dishwasher was bought in 1999 and this was the first problem I have had with it (April 2012), the appliance has been well used and is usually on once a day to keep pace with a family of 5.
Having read the comments on here I decided to have a go and fix the problem myself. Here is what I did:-
1. Disconnected the dishwasher fom the electric supply by unplugging it.
2. Removed the 'philips' screws holding the inner stainless steel door lining.Take care because the lower door may come away so support it as you remove the screws.
Once the lining is removed you can see the pipe that takes the condensate from the fan to a small drainage hole beside the detergent dispenser. On my model there is plastic part covering this so I can't actually see the hole on the inside of the dishwasher.
3. Carefully remove the pipe from the fan end first. I found this end the easiest to disconnect. Be careful not to stretch the end of the pipe. Then remove the lower end of the pipe to remove it. This was a little tricky as I did'nt want to force it off. It did come off with a little patience. My pipe was completely blocked with 13 years of grease and small food particles.
4. Wash the pipe in a bucket or sink in hot water and detergent (fairy liquid) to clear the grease etc.
5 Reattach the lower end of the pipe i.e. not the end beside the fan.
6 Without stretching the pipe attach a small funnel to the free end of the pipe and slowly pour in some hot water. This will flush away any build up of grease / food that maybe blocking the drainage hole.
7 Re-connect the pipe to the fan connection.
8 Re- fix the door. I needed an extra pair of hands to support the lower part of the door.
9 Plug in the dishwasher and switch it on.
It's been 3 weeks since I flushed my pipe, I have no water coming out of the fan vent when the door is opened and the fan now runs very quietly.
I'm hoping for another 13 years out of my dishwasher!!
I hope this helps as I found earlier advice on this site very helpful.
Richard
April 2012