Wiper Motor Problems

[staggerd86c-10]

Im in south florida and im not sure if you have seen the weather channel the last couple weeks it has been nothing but rain. My windshield wipers don't work for some reason and im not sure of what it can be exactly. if i flip the switch i hear the come on but nothing moves, but if i grab the wiper and pull it out it will work only once. could it be that its binding up or is the motor bad? i would like to troubleshoot this so that i dont have to buy any unnecessary parts. Thanks for the help