whirlpool awz 121 tripping electric?

Hi my whirlpool awz 121 has started tripping the electric when turned on. its an instant trip so need a starting point.I was told from blackwellsa that it could be heating element or thermostats?. all ican see is when with back and top removed you turn it on a spark comes from timer when it blows. ( i know this may mean nothing other than being the point that the electric cant go any further and pops.)
Any ideas would be appreciated. Always comes at bad time i.e little un being sick all night so loads of extra washing, drying etc.