Drain pump runs constantly

i have a electrolux A-120. the drain pump runs constantly, won´t stop even when there´s no water. the drain pipes are fine, the power is fine, no dirt in the way. when i turn it off and put water in and turn it on again it drains just fine, but drains constantly.
yesterday the machine was all fine, but when it was in the middle of the program the power went out because of the vaccumcleaner. after that the dishwasher just drains, no matter how i turn it on.