passenger window motor on 1993 GMC Safari

i have my window motor and when connected to a battery straight it goes up and down but when i cannect it to the plug it only goes up i have replace the switch what would be my next thing to do it is very hot and clamy in florida and this is aggravting my husband

1 answer
more than likely it is a wire issue, you need to trace out the wires and you will probably find a broken wire.