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 brake. Is there anyone out there that can explain what is happening with this machine? I'm so confused. Thanks,
The alternator produces three phase alternating current and the frequency varies with the speed of the engine, one of those phases drives the tachometer. If the alternator is not excited, it won't produce the alternating current to feed the tach, and the alternating current won't produce direct current to charge the batteries and system. I'd guess that the draw of the brake lights is the biggest power draw you have, and that's enough to drop the voltage to set off the alt light. I would check the connections at the alternator, at the console where the wiring goes through the warning light, and anywhere else you can find. obviously a wiring diagram will be helpful. You could also check the voltage of the terminals on the alternator and see if you can find what coincides with the tach working or not. Run a hot jumper for testing purposes to see if it starts the tach right away? That's all my best guess, I have an alternator that does the same thing with not starting the tach, but it's so random and lasts only seconds so I haven't tried
I have replaced the alternator and checked all connections but still not getting any charge to the battery or instrument panel. I am not very good with a voltmeter and don't really know what to look for. I checked the belt and pulled the instrument panel out ( lost half the screws ) and still can't get power. I disconnected the ground while it was running and it stalled. Earlier, I was getting fluctuating power to the tach but now I don't get anything. Help!!!
You should see 13V + at the battery when it's running. The same voltage at the big terminal on the alternator, and the same voltage at one of the smaller terminals to excite the alternator. Most likely you're not getting that excite voltage to the alternator so it's not turning on. You need a wiring diagram and a little luck to find and fix the, or a lot of patience and/or a lot of luck. I could be wrong about the tach drive, but the power from the ignition switch, through the instrument panel (battery warning light) and to the alternator is the likely suspect for not charging.
I can post more of the schematic if needed.