I just purchased this used 319D and am having trouble with the seat. When I got the machine delivered from auction the seat inflated but not horribly fast. I spent and afternoon cleaning the entire machine and the next day the seat is dead. I checked the fuse, it was blown, but every time I put a new fuse in it blows when I turn the key on, before I even get a chance to inflate it. I checked all the connections behind the seat, everything seems intact. Any ideas?