driver side power seat stopped working all of a sudden. how can i fix it?

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i had someone put in a new heater core and blower unit. my defrost wasn't working and the floor on the passenger side front was all wet. when he was done i couldn't adjust the power seat on drivers side. the mechanic said he didn't do anything to the seat but it worked before he worked on it. i just want to know how to fix the problem. thank you