1992 580 super k backhoe electrical trouble

I noticed when I start the backhoe that the tach doesn't work. After warming it up for a few minutes, if I rev the engine a few times, the tach kicks in. When the tack isn't working, the alternator isn't charging the system but once I rev it up a bit and get the tach working, the alternator starts charging. I changed the batteries and alternator and the belt is tight. When I drive the machine, that alternator light goes on every time I use the brakes and goes off when I take my foot off the...

1992 580 super k backhoe electrical trouble

1992 580 super k backhoe electrical trouble