Hello guys. I have a Case 580SK with an odd charging issue. The alt light does not come on, the tach does not work and it does not charge unless I briefly jump the terminal on the alternator to positive. I can immediately remove the jumper and it charges, the tach works, etc. until I key-off again. I assume there's a relay? Thanks in advance for any thoughts and insight; much appreciated!
The condition you describe sounds like the alternator is not getting electrically excited at key-on and therefore will not charge. The tachometer value is based on alternator output so it all ties together. On many vehicles the initial electrical excitation occurs through the warning light circuit in the instrument cluster. Therefore, the first thing to check is the alternator warning lightbulb, if it is burn out or contacts corroded, replace/clean/fix. Easy fix If light is good, check continuity in light wiring harness circuit from instrument cluster to alternator. A open circuit damage wire can produce the same behavior.