Have a 6 volt, front mount 8n. Installed new 6 volt headlights and rear light: they work fine. The ammeter has never worked, and the tractor works fine, no trouble with battery charging etc. Replaced ammeter. Ammeter does not move a bit when tractor is started: turn on the new lights, and it shows a discharge. This does not look good for snow plowing at night. What to do?? Thanks, PN.