Good Day all my old beat-up farm 200-6 excavator , the alternator hasnt been charging for 10 years [just been taking the batteries home after each days run .] Anyway finally trying to fix it so , obviously the BAT goes to the battery , the GRD goes to earth but , where should the third wire go to ? ie want to route it there directly rather than the existing wiring harness . Thanks all
Typically it will be fed voltage from the ignition switch, and through the battery warning light in the dash. For testing purposes, you can hook it directly to the "BAT", it will work fine that way if you disconnect the battery whenever it's not running. This is assuming you have an internal voltage regulator, if you had an external voltage regulator, there'd be at least two wires besides the BAT and GRD.
Thanks so it wont feed in too many amps connected directly ? or to be safe should i run it through a small watt warning bulb ?
Check the battery voltage when you start it up. But I wouldn't worry about it overcharging that way. The key switch and warning light are so it shuts off the battery drain when the engine is off, and to warn you if the alternator is not charging (could be the belt is broke, and you better know). Hook it up directly to test the alternator, then figure out the wiring harness.
Do that and you will be very sorry! The third wire on all Komatsu alternators that I have worked on is for the key to starter interlock which prevents the starter from turning when the engine is running. I also turns off the battery charge indicator light on the monitor panel and keeps the engine oil alarm from sounding until the engine is running. You will need a wiring diagram to put things back together right. The third wire has no voltage when the engine is not running. Voltage rises when the engine starts which matches voltage or the battery which means current cannot flow to turn on a light. If you hook a hot wire to the third wire you will likely blow the diode.
Listen to John C. I've never seen an alternator or interlock like that. edit: let us know how it works out. I'm not sure how that's any different than the third wire on any other alternator, except for the starter interlock being added into the circuit. The alternator still needs to be "excited" unless it's a one wire alternator with a "sense" wire.
I agree with the guys not to apply batt+ to that terminal. Typically there are three small diodes inside the alt that are attached to that terminal and there main purpose is to provide current to the internal field in the rotor. These diodes are small signal diodes and not heat sinked like the main diodes so excessive current or heat as they try to charge the battery in parallel with the Batt+ terminal will likely blow them. If you use a bulb between that terminal and the Battery should be fine.
This is for USA PC200LC-6 LC hope it it of some help.
Got it charging ran a wire directly from the BAT terminal to the positive on the battery and just left the third wire where it was -ie it just goes into the harness and who know where it goes , but anyway obviously that part is fine and it was the main heavy BAT terminal wire that was not connecting through to the battery
So anyway thanks for all the helpful and supportive comments