First post!! First dozer as well . . . . . . . . . 450G, no cab. Any tips on finding a wiring diagram? Alternator is not doing the job. I have 8V at the exciter wire with the key on. 12V everywhere else. That puzzles me!! Anyone have an explanation? The alternator light never comes on, even with the engine off. I do not have a good understanding of alternator lights, am tempted to install an old fashioned ammeter. Those I understand. This alternator appears to have never been touched @ 3200 hrs. No cab, I believe it to be the "smaller" alternator. Any insight would be appreciated. Jonny
Welcome to the forum Jon K. :usa 3200 hrs on an alternator? I'd be tempted to send it to an alternator shop. Probably time for a freshen up anyway with that many hours. 8 volts on exiter terminal? What's it do when you put a 12V jumper from the battery terminal of the alternator?
What is the voltage at your battery when the engine is running?
Hmmmm . . . . . now there is a thought . . . . . . Easily done, perhaps that would tell me something. Best I can tell, the exiter current is supposed to come right off of the switch. Maybe there are resistors in there? But would that reduce the voltage?
Just a bit over 12V if I did it right. I don't think I am charging at all. I will retest and report back, I am not sure that is an accurate figure.
Shouldn't be any resistors in the exiter circuit. Low voltage on circuit could be caused by a number of things, bad harness connections, failing ignition switch, worry about that after you put a jumper on exiter terminal and see if alternator responds.
Tomorrow!! If the sky doesn't fall . . . . . .
If you are only getting around 12v, your alternator is not charging. Normal voltage with the alternator charging properly is about 13.5 - 14.5 volts. Try a jumper to the exciter terminal from the battery, if your voltage goes up to the normal range, you have a bad connection in that wire somewhere.
do not have a good understanding of alternator lights, am tempted to install an old fashioned ammeter. Those I understand. Volt meter would be a better choice.
Ammeter works fine and lets you know if you are charging or discharging. Volt meter is good also. Like nortie above said it should read 13 to 14 volts if the alternator is working. If not the 12 volt reading will be coming from your battery and will continue to drop as the battery discharges. I suggest taking it off and going to the alternator shop with it. An independent shop to me is best. They will either rebuild yours, fix it if not to major and you are back in business. Stay away from Deere or any other OEM as you will get raped on the price.
I think I know what is going on ... the 8 volts on the exciter wire is probably right. I think your alternator has an internal voltage regulator. The exciter circuit starts as 12 volts at the key switch, then goes to the alternator light bulb (+). The light bulb has 2 wires, a "+" and a "-". The "-" side of the bulb is actually the wire you are measuring 8 volts at. The exciter terminal on the alternator connects internally to the + brush. When the engine is first started, the alternator uses the 8 volts to excite the field and make the alternator start charging. The internal regulator takes over from there. The light bulb acts as a resistor, and limits the initial alternator output. Once the engine starts, if the regulator is working, the + brush will have voltage on it, and the alternator light will have 12 volts on both +/- wires, so the bulb won't light. If the regulator isnt working, and the brushes are good, the alternator light will find ground through the brush circuit, and the bulb will light up, signaling a problem. If the brushes are bad, the alternator won't charge, and the light won't light, so you won't know til the battery is dead. I know this sounds complicated, cuz, well it is, LOL. Bottom line, I think your alternator is bad, more specifically, the brush circuit is probably open. Just for fun, I'll bet if you remove the alternator light bulb, you should lose the 8 volts @ the exciter terminal.
Jon, I dont know how old a G is but exciter current could come from an engine monitor. If current goes thru bulb and bulb does not lite, there should not be any current at alternator. Jump exciter will tell you right quick, I think alt is bad but verify first.
Thank you guys for the replies. Sorry i have been away, the sky fell on me, as it always does. Bolt thrower, I'm sorta like the Slingblade guy, I don't understand all of it, but I understand a great deal of it . . . . . Finally got time to spend on the dozer Saturday. 12.2 volts on the battery enginer off. 12.2 volts on the battery engine running at a good clip. Definately not charging. 8 volts on the exciter terminal is real. But the light is not burning at any time. Weird. The schematic that I have has the exciter voltage coming directly off of the keyswitch, directly off of a 12V power source. Should be 12V. But it ain't. Not completely sure I have the right schematic. I show the alternator light wire going to a completely different terminal, and must be some magic at work to make it burn or not. Regardless, I jumped 12V directly to the exciter terminal and still nothing. Going to pull the alternator off tomorrow afternoon, and get it to a shop in McComb Mississippi. Supposed to be good people, I will report back in a week or so.
I had alternator trouble on a tractor and was going to take it to a shop but figured it was no good anyway and all they do is give you an exchange so I decided to take it apart myself. Quite simple really, put new regulator, brushes, had the armateur put on a lathe for a clean surface that wouldn't wear the brushes, new bushings. The whole deal cost me $14 and the alternator is still working good after many years. Now I fix all my alternator problems myself.
OK, this took waaaaay to long, but I did get the alternator working. Took it to the abovementioned alternator shop in McComb, Miss, but they came to the conclusion that they couldn't get parts for it, it was to be scrapped. Got a shiny new on from the same guys, got it bolted on. Had to call them to figure out the ground, exciter, alt light, etc, but after I got it wired up I had dang near 15 volts when running, so a new alternator shore fixed it up!! Only good news is that the guy who sold the dozer to me deals with these alternator people all the time, and felt remorse or something so he picked up the bill!!! Thanks for all of your help!! I am a tiny bit smarter now!
Good to hear ya got it sorted out.