I have a case 590 super m series 2 Serial no n5c394470 and I’m having an issue with the tachometer not working and the charge light stays on even though the volt gauge goes to green when started and I’ve checked the voltage at the big wire at the rear or the alternator and it’s 14.4v while running. Battery connections are clean and tight as are the alternator connections and no obvious wire damage. I also pulled the gauge cluster and the wires and connector look fine took the screws and back cover off and everything looks like it should no corrosion or burnt looking resistors or diodes etc.. I just bought this machine so I don’t know any backstory about how/why/when it happened. I do have the operators manual and have ordered a service manual and parts book but it’ll be a few days before I get them and thought maybe somebody has ran into something like this before. Thanks in advance for the help.
If it is an electric tachometer, there is a good likely hood that your alternator is not sending the AC voltage to the Rpm gauge or the connections in between are faulty. Yes it would run on AC not DC on the ones I have seen. Would be handy if you had a schematic of alternator to Rpm gauge. Simon C
Yes I’ll probably just have to wait till my service manual gets here so I’ll have the wiring diagram.
Post a close up picture of the back of the alternator wiped clean, and maybe can suggest a few tests. Simon C
I found a little more info in some other threads and have done these tests with no change. I’ve checked the yellow wire out of the alternator which had 7.8vac while running then ohmed checked the yellow wire to pin 19 in my gauge cluster which was good at .003 ohms then checked the volts at pin 19 with it running and it was 7.7vac.
One of the small wires coming off that plug will produce AC power to run the tachometer from what I remember. Back probe all three wires with the unit running to find out which one it is. It usually is the center of the Y - Stator output with the black test lead going to battery ground. Maybe that wire is disconnected or bad connection back to tachometer. Center is probably the wire that you posted as 7.7 volts. Don't have a schematic to confirm. Simon C