Hey folks, hope y'all are well. My tacho may be on its way out. It works absolutely fine for about 15 to 30 mins and then drops to zero. No change in the running of the bike, so I don't suspect any ECU issue, I only notice when I glance down. I thought it might be a loose connection, but once it's dropped to zero, it stays there. However, stop the bike and immediately restart and it's fine again...for about 15 to 30 mins. The thought has occurred that a loose connection might cause a wavering signal to the logic within the tacho unit and that causes it to just start ignoring the wavering input (i.e. the drop to zero reading). I know of more modern silicon that might behave that way if an input signal can't be trusted, but not sure in this case. However, if it does then that would be consistent with a power reset then resetting the logic and it starts reading normally until the input wavers again. However, I'm not sure if the IC logic within a 916 tacho works that way...does anyone know? It's not causing me a major issue, as I can hear/feel what the bike is doing, but it would be nice to have a fully working unit. My thanks to the hive mind for your thoughts
Electronic tachometers give erratic readings when the base voltage is low, usually caused by a loose or corroded battery connection — so check this first. There are three brass screws that make an electrical connection on the back of the tach. These loosen up and cause erratic readings. Sometimes if you push on the tach lens, it'll momentarily go back to functioning normally. If so, tighten them up (not too tight or you'll damage the unit). See Also, http://www.ducati.ms/forums/40-sport-touring/140971-st4s-rev-counter-tachometer-repair.html
The rev counter not registering is usually the first sign of a faulty voltage regulator. When the voltage drops below some figure the rev counter stops working. Check the battery voltage when the bike is running, both at start up when the recounter is indicating and again after it has stopped working. It is worth checking before doing anything more drastic.
