One thing that you can check are the wires coming off the alternator, sometimes there can be corrosion were the wire is crimped on to the terminal. I have had this happen on my 873. My loader would not start all the time. I had checked the switch,relays, checked wires for continuity. My father is an electrical wizard, one of those men that think about problems on a different level. He said to check what I checked. I told him I already checked them. He then said check the wires at the power souce, the alternator post. I said I already checked them, He said no youdidnot, If you did you will find oxidation on the wires probably were they are crimped. He said to open up the crimp and look. I did, sure enough corrosion. I cut off the connector, crimped and soldered the new terminals as told by my dad. End of problem. The only way to see the corrosion was to open up the crimp. Thanks Dad! Rich M-37Possibly a bad exciting wire from the key switch. With the key on, you shoudl be getting 12v at the exciting terminal on the alternator.