sounds possibly like a water level related issue. there should be 2 settings on a pressure switch. 1 is to determine when the machine needs water (ie low level) and the other is to indicate high level. the machine should also have a timer to stop the machine constantly filling in the event that the level switch fails. these two things together will manage a set level. if the high level part of the switch is faulty, then the machine will default to the timer. therefore on half load there will be the same ammount of water put in as on full load, only the actual level will be lower.
tony, January 2009