Amp question

Years ago I added more lights to the old JD 8430. Since then it has always had an issue keeping up if I run them all and the A/C. I always
figured I was out working the alternator so it didn't bother me a lot. The alternator hadn't been touched that I can remember so I should just
have it refreshed. Anymore I don't do much night farming so I don't worry a lot about it. If I do I just high idle it for 30 minutes with everything off
and it will start the next day.

Anyway, the dash only has a volt meter. Is there anywhere I could stick in an ammeter to see what is going on? This is just for curiosity sake so
I don't care if it's on the engine. If I do it off the back off the alternator I will only get charging but I guess I can see what it maxes at and see if it
is putting out rated amps. I'm just betting it isn't. It charges fine with just daytime loads, but the lights push it over the edge. The funny thing is,
there are only 8 regular tractor lights total. The IH 886 has the exact same everything and has no issues at all. Who knows, there may be a
ground issue.

Voltmeter should tell you all you need to know. You probably have a 80-90 amp NippoDenso alternator that can make 30-40 amps with the engine only at idle speed. That's a lot. The only true way to test is to put a 80-90 amp load on it and see if it can keep up. It is kind of unusual for an alternator to make "low" output. "NO" output is more common. But if one or two rectifiers are burnt up - low output can happen.

The easier thing to do would be to switch some of the lights over to LEDs. They draw fewer AMPS and have a better light color. I just buy them off Ebay and have had good luck with them. I use two different style lights. The one is a five inch round light that works well for replacing the round lights on the fenders. Then the other is a 7 inch wide light that works well on light bars and such. This place ships fast. Usually in just two days to me.

Five inch lights are $10 for two complete lights:
http://www.ebay.com/itm/252202354484?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Seven inch lights Are $15 for each light. I buy them 8 at a time for $120:
http://www.ebay.com/itm/252312904939?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Five inch lights

Seven inch lights

If the volts are not keeping up, then amps aren't either.

I would first check belt and pulleys.

Hello notjustair,

You answered your own question! A larger capacity alternator is in order. An amp meter will only tell you the rate of charge...useless. A volt meter will tell you when the battery is fully charged.
Stepping up the alternator speed can be helpfull, but I would also recommend that you check the belt tension,

Guido.

I would change out lighting to LED before upsizing alternator, not prudent to add amps without upgrading wiring.

Hello David G,

Tractor's R.P.M.s are no way near the automotive speed, so a lttle faster should not be too detrimental,

Guido.

Could downsize alternator pulley.

If you already have an 80-amp plus alternator, going bigger would be silly. That unless you are lighting up a football stadium. I have no idea what your total current draw is. One note though. Deere tends to derate the alternators by installing large drive-pulleys. So if the alternator is otherwise working as it should, a smaller pulley like used on a car might be all you need.

As it is now with the large Deere 3.2" pulley, it should be working like this.
800 engine RPM - 28 amps, 1200 engine RPM - 52 amps, 2000 engine PM - 72 amps

If you put the standard 2.6" automotive pulley on, it works like this:
800 engine RPM - 43 amps, 1200 engine RPM - 65 amps, 2000 engine PM - 80 amps

Thanks for doing the math

Hello David G,

Even 1/2" would do the trick! Would not hurt a thing.......

Guido.

As previously stated....Low engine rpms, partial failure of the alternator, worn fan belt and worn alternator pulley, worn water pump pulley and worn crank pulley. compare all those to new and you will be amazed at the wear. Don't super tighten the fan belts as this will only ruin the alternator and water pump bearings.

Lots of good advise, especially going with the smaller pulley.

The volt meter should give all the information you need. If the reading falls as you turn on more lights, then it is not keeping up. Adding an amp meter can be risky on a high amp alternator. It can be a source of resistance, robing some amperage from the battery, and prone to the connections getting loose and overheating.

I think that is a Delco alternator. Do you know if it the original? If it is, it should be a good size, like an 80 amp or so. It is possible that if it has been replaced with one from the auto supply that it may be a smaller amp, like a 35, 40 amp. They are stamped on the case, but that isn't always correct if it came from a rebuilder.

You can take it off, go to the auto supply and have it tested. The machine should be able to test the output and the integrity of the alternator components. There is a small inexpensive component inside called a "diode trio" that commonly fails. When it does, the output drops, but it will still work, as you described, at a lesser rate.

Something else to check is the belt tension and condition, (a rule of "thumb" is to use your thumb to push on the alternator fan, if it slips the belt, the belt is loose or worn to the bottom of the pulley and should be replaced).

Next, with the engine running at speed, and the lights and accessories on, check the voltage at the stud on the back of the alternator to ground. Then compare this reading to the battery voltage across the posts. If there is a major difference, like 16v at the alternator, and 12v at the battery, then there is high resistance on the wire from the alternator to the connection with the battery. Look for heat discolored connections or corrosion on a connection.

The voltmeter should tell you all you need to know. If the voltage stays over 13.5 volts under full electrical load, the battery is charging. If it drops much below that you have a problem. An ammeter isn't going to tell you much, because even if you are able to locate it where it will show the net charge, it's hard to tell the difference between +2 and -2 amps. And if you put it at the alternator output, you won't know if the alternator is keeping up with demand.