Alternator or batteries or both?

ever since I had this combine, about 6 years, The alternator does not charge until you run the engine wide open for about 30 seconds. Now it never charges no matter how long or fast you run the engine. hence the batteries go dead. Question! Are the batteries dead because the alt is not charging or is the alt not charging because the batteries are dead? I have never replaced the batteries so they are at least 6 years old. So if I get new batteries will my alt start working again? or do I need a new alt?

An alternator will not charge if the battery is completely dead. Charge the battery and see if it starts to charge. It takes very little voltage to start an alternator to charge.

If those batteries sat over winter without a charge and froze up, it's a good bet that you need batteries.

Don't know why, but a frozen battery just never seems to recover from the freeze-up. They might 'seem' okay to you just working with 'em, but they cannot take a good charge anymore.

Now, that alternator should at least 'try' to fill 'em up. Maybe ya need both?

Just my opinion,

Allan

Replace the batteries and once you get the engine running use a volt meter and see what your charging voltage is across the battery terminals. Run the engine at 1/2 throttle or better. Should see 14.0 to 14.5 volts on a 12 volt hookup. If you're seeing only 12 volts your alternator is the problem. You could try try charging the old batteries then check the charging voltage. Hal

Like Hal said, the handiest tool I have for this is the volt meter, with a load switch. Harbor Freight has them for $20. Take the batteries out, give em a decent charge, hook up the meter and flip the load switch, that will tell you whether the batteries are ok or not, that needle will drop way lower than 12 volts. Without a load on them, they ought to be at 12.5 volts, and when you place a load on them, the needle should not drop off by much.

You can test the alternator with the same tool, just start the engine and unhook one terminal of the battery, hook up the meter and see what it reads. I believe (someone correct me if not so)that if the batteries are hooked up and dead if you do this, it may not show a true reading, because said batteries act like a short and draw too much ? I thought that you need to spin the alternator without the batteries hooked up to see what the output is, auto parts stores used to have a machine to spin them to see if working properly or not.

I know on a charging system that is working properly, batteries good etc., just hook the meter up while running, should read 13.5-14.5. like was said. Anyone who has multiple vehicles, tractors etc. would benefit from one of these $20 meters, I kept an old one from our old dealership and bought a HF one for the farm, very useful and inexpensive tool to have.

Don't ever unhook a battery cable while it is running. You will have more electrical problems than what you have now. If the batteries have enough charge to get it started, the alt should charge. Male sure the belt is tight.

Probably not a good thing to unhook is it, always a spark, other issues to consider, I would also highly recommend eye protection and ear protection any time one is fooling with batteries, in the event of overcharging, plugged vent, sulphuric gas etc.

Unhooking a battery cable when it is running is a good way to cause many other problems. #1 you can/will let the smoke out of the alternator. #2 if you get between the alternator and ground etc it can shock or if you have heart problems even kill since an alternator can/will put out more then 90 volts and more them 35 amps which by the way is 35 million more maps then it takes to kill since it only takes a Milli amp to kill a man as in one millionth of an amp

Sounds like you have the common problem child 1 wire alternator on it and if so replace it with a 3 wire that is wired correctly. As for which one is causing the problem take them both in and have both checked which most auto parts stores will do for free and then you know but if I where to guess I would say you have 2 problems both the battery and the alternator

It would help if you gave us a little information, like what combine(year and model) and what brand /type alternator. It is very important to know this to give you any info that is not just a wild guess.

A 1 wire Delco alternator, if that is what you have, should excite at the high rpm most combine engines run, but if it does not, no need to replace it. A 1 wire delco SI series allows you to wire it exactly as a stock 3 wire Delco SI series IF you need a charge indicator light or need it to excite at lower rpm. They operate the same when wired as a 3 wire system.

Yes, I recall this is not good practice, bad advice due to other problems, but I think what I was getting at was, if the alternator is still on the engine, but COMPLETELY disconnected, (all wires) except the belt, shouldn't you be able to test it's output as stated with no harm or other problems. I would seem to be the same thing as what the auto parts places, starter/alternator places do to test same.

I recall having an old connection fail after installing a new 350 in a K10 chevy. Failed at a "Y" connector, alternator was not charging, installed another, no good, returned same, brought 2 friends over to add a few more "eyes" to help search/test etc. and shortly after found that failed connection, which obviously let the "smoke" out, effectively doing the same thing I mentioned here, how soon we forget !!!!!

The test bench at the auto parts store does in fact put a load on the alternator so as to get a true reading of what it is or is not doing. Unhooking one unloads it so the VR in it then goes to max charge and that in turn smoke tests the diodes and that in turn leads to it putting out true AC at up to and over 90 volts at a high amp which like I said can kill. In the military if your where to test one that way and the wrong person saw you you would be put on report and that can cause a big hurt in your back pocket.

Same thing as when the VR fails and causes a short, draw down on your battery then isn't it ? I'm wondering where in heck I ever thought that was ok to do, they do test em with a load on em. Well bad advice on my part, but always something to learn ... don't try this at home folks LOL !

The reason I know this stuff is because many years ago I had a guy show me what happens and the volts and amps that an alternator can produce when unhooked from a battery. As for the part about the military I also found that out the hard way and almost got put on report but talked the guy out of reporting me

I can see why the concern due to voltage, and the fact that when working on something, you use both hands, creating a circuit across your heart, is also why I've been told to use one hand when working in a live electrical panel, which I would assume to be a valid thing to practice when doing so.

You can read all these messages and not find your problem. Have someone who knows how to test your system to see what is actually wrong. With electrical systems on vehicles there can many problems from battery to alternator and every thing in between. One thing that you can do without any testing equipment is take your cables loose from the battery and then take a good sharp knife and clean the terminals if you get a hard surface that crunches as you clean this is most likely your problem . They should very shiny when cleaned like new lead surface not black or dirty looking.
Walt

Ya even when you use one hand it can hurt big time but then I did that type of stuff for years.