Finally got rear wiper motor going but i'm thinking there's either something wrong with the arm, or it might be the wrong one (it was on the top when I bought it from the original owner though). The mechanism is simple, right? Pull the arm out to 90 degrees off the glass, then pull the tab to take it off. BUT, mine doesn't hold at 90 degrees, in fact the spring is so tight that I'm sure if I let it go it would smash the glass. Is this normal?