My speedometer won't go back down to zero. It stops at about 12 mph. When I drive it, it will give me what I think is the correct speed. But then when I slow down to a stop it won't go down to zero.

 

Get a GPS speedometer app on your phone and see how it compares. I have had one speedometer go bad. They are magnetically driven. I also had one read above zero and I pushed the pointer back. I had to take off the clear cover. You can gently spin it back on the shaft. You'll have to check it against GPS again to see if it's accurate. If it is accurate above zero. I'd leave it.