How can I fix my Miele G641 that isn't washing? (Inlet/Drain)?

Hi,

I've been given a Miele G641 Plus dishwasher that's been sitting in someone's garage for about a year. Apparently it worked fine when the previous owners took it out of their kitchen but I've plumbed it all in and it's not doing what it should.

When I turn it on the green light flashes and after selecting a program and pressing start it begins whirring and then drains water out. After draining, it then starts sucking water in and I can hear the Miele Aquapump working on the cold feed pipe. After a few seconds of filling up, all noise stops and all I can hear is a quiet humming and an occasional click from inside the front panel near to the program selection switch.

I've taken the panels off of the dishwasher and when it runs it's possible to see the water drain out of the bottom half of a plastic pipe on the left side that runs up into the top of the appliance (looking from the front). Then, when it takes the cold water in it's possible to see the plastic tank on the right side filling up (the bottom of the dishwasher fills up with a small amount of water inside) I've checked the bottom float switch to make sure there was no water in there (- there wasn't) and I've taken the Aquapump connector off and reconnected it to make sure there wasn't a loose connection after transporting it.

When I got the dishwasher there was a small amount of water in the bottom inside, which drained as soon as I switched it on (but then subsequently refilled when the water was pumped in!).

If anyone has any ideas then let me know, I'm happy to try anything! I've heard a rumour about a float valve that could be stuck inside the dishwasher but I can't seem to locate it and the bottom is moulded plastic so I can't even take it apart to try!

Thanks very much in advance