The speedometer in my '92 Mazda MPV recently started making a very loud whirring sound and the needle started to bounce up and down when I would reach about 30 mph. I took it to my mechanic and he said it was the speedometer cable and he replaced it. For $200, part & labor. I had it back for two days when the sound and erratic needle bounce returned. It's back at the mechanic's and I think it must be the speedometer itself causing the problem, not the cable. My question is this: If he replaces the speedometer and that takes care of it: should I just pay the additional cost for the speedometer and labor and let things be? Should I ask him to deduct the cost of the speedometer cable replacement because he misdiagnosed the cause of the problem initially? What would you do?