My hour meter reads a minus 86.7 I someone posted that the polatity was hooked-up backward. This is very unlikely in my case. The hour meter has never been unhooked and ran fine from the beginning. I have changed the battery but I now the difference between + and - and Red and Black. As I understand it, the hour meter monitors the time between oil changes. If true, how does it know. Also, I have just changed the oil and filter and it did not re-set the meter. Someone please give me some schooling on this issue.