Lots of things, Mains filter, could be shorting, as the m/c takes more power, water valve/s, as they are one of the 1st to operate, after the programmer, You would need to disconnect things to find out. Mains filter, you would need to bypass it, so if not sure get someone in, water valves, you could pull a wire off, keeping it well away from anything else, then plug m/c back in and try, if does not blow, water valve, replace
SD, July 2012