hi 2 possible problems.....
1.....the programmer/control is not correctly controlling the hot water inlet valve hence letting water in but not stopping it when it has enough...
2.....the pressure switch system is blocked/got a hole in pipe...hence not getting the right signal to shut off water in it has the right amount in the drum....
if no.1...can be quite expensive....
if no.2 ..reasonable cost of repair...
a good company should be able to find fault and point you in the right direction..hope this helps many thanxs
wolf359
September 2005