Check to see if the circuit that the washer uses is a GFI protected circuit. It may have the GFI stuff in the outlet, in the outlet of another socket on the same circuit, or in the circuit breaker panel. If so, temporarily run a 12 gauge extension cord to a non-GFI protected circuit and see if you still have the problem. If not have the GFI circuit replaced.
GFI protection circuits can start to go bad on an intermittent basis being tripped by a high load like a washer or hair dryer.
If this is not the problem, measure the current draw before the breaker goes to see if it is above 10 amps. If so then its the washer. In this case, have the service guy remove the motor connections and try again. If it still blows the breaker then it's not the motor and you have a short to ground somewhere like to the case from an exposed wire, or another component has failed.
George |