I have an older skid steer (94) with a Kubota engine. The alternator was changed to a 2 wire Prestolite because we couldn't get a an electronic voltage regulator to work with the original alternator. Old style regulator worked but no longer available. The new alternator doesn't charge at idle after start up but once the engine is revved up the alternator works fine and will charge when put back to idle. Everything was working fine till last weekend when the fuel gauge stayed on full after using the machine for 2 1/2-3 hours. I discovered when I turned the key off (doesn't stop engine) the fuel gauge went down and appeared to show the correct reading and the alt. light came on as it should. If I shut the machine off (with the throttle lever) and then turn the key off, the gauge will drop to zero and the alt. light would come on like it's supposed to. Playing with it some more I found when it doesn't charge on initial start up and the alt. light is on, turning the key off makes the gauge go to zero. Once I rev up the engine to turn the alt. light off, turning the key off makes the gauge appear to read the correct level. Machine not running, turning key on, gauge reads full. Hoping some of you electrical guru's might have an idea what's going on. I think the gauge and sending unit are fine and it's a weird wiring issue but don't know where to start.
I'm a little suspicious of the alternator hookup. A one wire alternator should act like you describe not starting to charge until it's revved up. A two wire alternator should charge at idle right from the start. The first place to check after the alternator is any ground connections on the "instrument panel" or whatever you have. It kinda sounds like something is being fed power from two sources, or backfed or something like that, just not sure if it's a ground issue or the alternator hookup.
It was working good so I think it's a ground issue too, just hard to figure out where.
I think it was a stuck float and seems to be working now but have another problem. What would cause the starter to start the machine when cold but when hot after shutting off for a few minutes doesn't turn it over fast enough to start? Appears to be charging so I'm wondering if the batteries could be bad?
I've had starters get too hot and lose their power and was told it's from windings shorting out but when cold they work just fine... at the time I didn't want to mess with it so just changed them out and was good however the first step I usually do is check/clean all connections to the starter just to eliminate the simple fixes
It spins over fast when boosted so that's why I think it could be the batteries but I'll do some more checking when I go out to my land again.