I am new here and need some advice.I have a 69 chevy pu and just recently bought a new rebuilt wiper motor. I thought it was a 3 prong but it ends up being a 4 prong. will this make any difference as on of the prongs wasnt hooked up anyway. It appears that someone worked on it before as the arm that is at the top of the motor was welded so I am in need of another arm and if anyone has one to get rid of I would GLADLY purchase it. Thanks for your help in advance.