vac stumbles when light switch pulled out part II

This is part two of my 51 vac running slightly rough when light switch is pulled out to 2nd or 3rd position. I looked at the wiring diagram and traced it back one more time. It all looks right and the wires are in great shape. This is assuming on the light switch the wire at the end of the fuse goes to the ammeter, the middle top goes to the lights, and the one down by the resistor goes to the generator. This is how it looks in the diagram. I then started with the trouble shooting diagram. Step 1, with the tractor off, pull turn on the lights. Ammeter should show discharge. Failure at step one, I think. The needle jiggles just a little but doesn"t show discharge. THen, I think, well I have all LED"s so maybe they don"t draw enough. THen I think, the red blinking light is not led so i turned it on with the lights figuring that should draw enough to make the needle move, but it did not. So, I would say I need a new ammeter. That brings up the idea of replacing it with a volt meter. Will a volt meter work with that charging set up? and with pos ground. Thanks again to all who have chimed in in the past. I have another problem, but that is another post.

Voltmeter will work with any system, if it's pos ground then + side to ground. It does not hook up like an ammeter and does not replace it, although you could put it in the same hole. Normally a voltmeter is connected to the ignition or acc terminal of the keyswitch, other side to ground. Personally I like to have both working when troubleshooting, so I'll just hook up a handheld VM and watch the dash gauge. I recommend you get and use a cheap handheld and use it before you start throwing parts at your tractor, you can burn up a bank account in a hurry that way.

I do not think your problem is the ammeter. Run a jumper wire across the two terminals and try it. If you have all but one LED lights you are not drawing 5 amps total to the lights. A hand held volt meter on your ignition wire to your coil while you make it stumble will tell you if it is an electrical problem. I would suspect something in the generator cut out control which is connected to the light switch.

Is the light switch and ignition on in the same as in one positon for ignition and the next for lights?. Next what does your amp meter read?? If it reads say 30 amp max then yes your lights will not move it much if any. But if you where to take a jumper from the non battery side of it and short it to ground just for a moment I bet it would jump to max discharge if it is a good meter. On one of my machines I have the ignition switch and lights on the same switch and also excites the alternator that way. one position ignition is on next position lights are on and also excites the alternator. Push it back to ignition and lights stay on and alternator stays excited.

I will try grounding the ammeter.

Just use a passing sort of grounding as in do not hold it so much as more then a second while watching the gauge. You should see it peg and then as soon as you off ground again go back to center. Hold it long and it can burn out the gauge