Alternator issues....

I have a diesel power unit on a pivot. The alternator quit working so I replaced it with a reman one. Fired up engine and the alt. was putting out 16V and the amp gauge was pegged out a 60+ amps. After about 2 minutes the alt. started smoking so I shut it down right away. Alt was toast. Put another oe on and fired it up and was charging 14.5 volts. But amp gauge was still pegged out. Thought it might be ok. NOT... after a few minutes this alt started to smoke as well. Any ideas what might be wrong? possible short some where. The battery still had 11.5 volts enough to start the engine. Someone told me if the battery was completely dead it might ruin the alternator. This is not the case. Any ideas as to what might be going on? Thanks funtwohunt

A 11.5 volt reading is pretty darn dead if that is open circuit voltage test. Cranking voltage would be good with that reading. Never good idea to rely on an alternator to recharge a battery. They are supposed to be able to charge full charge but have seen way too many fail under those circumstances. Way too many. Recharge your battery or temporilly replace it with fully charged one.

A full charged battery should read over 12.5 volts and anything lower is a battery that is way low. The voltage reading you say it has is a battery that is more then 25% discharged. So you may have battery that has a dead short in one of the cells which can/will fry an alternator. Or you have a short some place in the charge circuit which will also fry an alternator

(quoted from post at 23:00:15 06/27/17) I have a diesel power unit on a pivot. The alternator quit working so I replaced it with a reman one. Fired up engine and the alt. was putting out 16V and the amp gauge was pegged out a 60+ amps. After about 2 minutes the alt. started smoking so I shut it down right away. Alt was toast. Put another oe on and fired it up and was charging 14.5 volts. But amp gauge was still pegged out. Thought it might be ok. NOT... after a few minutes this alt started to smoke as well. Any ideas what might be wrong? possible short some where. The battery still had 11.5 volts enough to start the engine. Someone told me if the battery was completely dead it might ruin the alternator. This is not the case. Any ideas as to what might be going on? Thanks funtwohunt

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Regulator circuit is not sending system voltage to alternator regulator .

What the others said is all valid. First thing you need to do is charge the battery. In this day and age it is not out of reason to get a bad "rebuilt" alternator, it is also not out of reason to get two of them in a row from same supplier, I have been there. That being said your low battery did not cause alternator #1 to over charge at 16 volts. It MAY have cause alternator #2 to smoke due to being poorly rebuilt. The regulator is supposed to limit both voltage AND amperage to protect both the battery AND the alternator but cheapo rebuilds often will not stand full outputs either. A short of the magnitude you are talking about, 60 amps plus, would completely kill the battery in no time with the charging system not working,I dont think a short is your problem.

Fun, when you say " The battery still had 11.5 volts enough to start the engine"

I would say that was NOT a battery stabilized and at rest IE it was too soon after receiving that high charge.

FYI A "good" flooded lead acid battery AT REST AND STABILIZED FULLY CHARGED AT 77 DEGREES SHOULD READ 12.63 VOLTS....If its ONLY 12.5+ volts it's partly discharged. NOTE if your voltmeter isn't accurate that's your problem, below are correct voltages.

100% Charged = 12.63 Volts
75% Charged = 12.30 Volts
50% Charged = 12.00 Volts
25% Charged = 11.76 Volts
0% Charged = 11.64 Volts

Those abnormal high voltages may be because the voltage regulators VOLTAGE SENSING CIRCUITRY isn't connected to monitor correct battery voltage so its running wide open or else its toast or simply not wired.

A possible short somewhere in the regulation or charging circuit could cause a high current draw. Maybe a short is overloading the alternator and all the current isn't getting to the battery itself??

I suppose some battery problems could possibly cause a high current draw, I would take the battery to a shop for a proper LOAD and voltage and specific gravity test to insure battery condition BEFORE SMOKING MORE ALTERNATORS.

Is this is three wire or a so called "one wire" alternator as it doesn't appear to be sensing battery voltage correctly. It may not be wired correct !!!!!!!!!!


John T

Here is a pic of my alt. The power unit also has the typical Murphy protection setup. Thanks

Pic

More info on the alternator would help. I cannot find any photos in your posts although they indicated you posted images. I tried the "old view" and "modern view."

An alternator and regulator combo - should not be able to ever exceed 14.2 volts (more or less). It does not matter how bad the battery is. Also, an alternator should be capable of making whatever power it is rated at. If you have, let's say, a 70 amp alternator - and run the engine at full rated speed, it will be capable of making 70 amps until voltage rises to 14.2 volts and then cut back. It should not be cooking itself. Granted, a bad battery that demands high capacity from the alternator without ever reaching 14.2 volts won't last as long as it should. Not melt in 5 minutes though.

It sounds like your alternators have been "full fielding." What kind of alternator and where is the regulator,IF there is one? I know some have no descrete regulator and use a part of the main control computer instead. I have a generator like that. Also some new cars and trucks are also like that. Even my 2001 Dodge Grand Caravan has no stand-alone or internal regulator.

Now maybe a pic

From that pic, it 'appears' to be Delco 10-SI, & also appears that you have reversed the Sense(#2) and Excite(#1) connections.

On the 3 wire 10SI Family of Alternators the 2/F small (that 2 terminal white plastic connector in picture) side terminal is VOLTAGE SENSE. It needs jumped to the big rear main output terminal to sense voltage and therfore correctly regulate charge rate. The other small 1/R terminal is the excitation circuit and requires initial excitation voltage.

IF YOU HAVE THE SMALL 1/R terminal jumped to the rear main output THAT MAY BE YOUR PROBLEM. The 2/F is what's jumped to the big ream main output stud

Is the small white plastic connector installed bass ackwards???? so the two small terminals are on the WRONG terminals???

INSURE 2/F IS WHATS JUMPED TO THE BIG REAR MAIN OUTPUT STUD AND NOT 1/R

OF COURSE the Alternator is most likely NEG ground, you're wired that way correct?????????

John T

BASED ON YOUR PICTURE

On the 3 wire 10SI Family of Alternators the 2/F small (that 2 terminal white plastic connector in picture) side terminal is VOLTAGE SENSE. It needs jumped to the big rear main output terminal to sense voltage and therfore correctly regulate charge rate. The other small 1/R terminal is the excitation circuit and requires initial excitation voltage.

IF YOU HAVE THE SMALL 1/R terminal jumped to the rear main output THAT MAY BE YOUR PROBLEM. The 2/F is what's jumped to the big ream main output stud

Is it installed bass ackwards???? so the two small terminals are on the WRONG terminals???

INSURE 2/F IS WHATS JUMPED TO THE BIG REAR MAIN OUTPUT STUD AND NOT 1/R

John T

Looks like were on the same page yayyyyyyyyyyyyyyyy

John T

Yes, it is wired wrong. You have the "sense" and "excite" wires switched around - as the other poster noted.

Still odd that is burns up that alternator so fast. Is it a 10SI (steel pulley) or a 12SI (plastic pulley)?

I asked because I recently put a 12SI into my 1978 Toyota motorhome an had those two connections switched. It charged at 15.5 volts all the time but did not hurt the alternator. I drove it 40 miles before I realized I had it wired wrong. A 10SI is less rugged though.

When you fix the wiring, instead of running #2 to the output post, the system will work better if you run #2 all the way back to the positive post on the battery where it belongs. Many just run it to the output but that does not work as well unless the battery is only a foot or so away.

We had just set this unit about a month ago and I left the wiring like it was on the old unit with Sam alternator but it must have been wrong from the get-go I greatly appreciate all the help guys I will tackle it later this afternoon and let you know what I come up with thanks again

Thanks for the feedback. Being its a diesel instead of a gas engine the wiring methods used to provide initial excitation voltage to the alternators small side 1/R terminal can vary a lot and still work, but its not rocket science and perhaps ? its wired to work already ONCE YOU SWAP THE TERMINALS on that white plastic connector ? I have seen oil pressure switches or various other switches and methods used on diesels to send excitation voltage down to 1/R on the alternators side. Can your white plastic connector be changed side to side so wiring is reversed and still plug in or not????? I've seen plastic tabs that prevent reversal while I've also seen some (maybe jury rigged??) that can be reversed. Most guys just jump the small 2/F terminal to the big main rear output on the alternator and it works fine. As a used tractor dealer I've seen hundreds working okay wired that way while the actual battery voltage on the terminal could be slightly different and wiring instead to the battery could be better. Either way will work.

I didn't take time to go look at a 10SI Alternator to see FOR SURE what side is 1/R and what side is 2/F and NOTE my and others explanations are assuming its wired wrong YOU HAVE TO LOOK AT YOUR ALTERNATOR TO MAKE SURE and if its NOT as were thinking we all have to go back to the drawing board lol ITS THE 2/F TERMINAL THAT SENSES VOLTAGE AND IS WIRED TO THE BIG MAIN REAR OUTPUT STUD OR BATTERY

John T

TRied to fix alternator problem today. Checked a lot of the things that were suggested. Put new alt on and with out hooking the 1 or 2 posts as suggested., just hooked up output wire. When I started the engine it pegged the amp gauge to the charge side. Shut it down immediately. Going to get someone that knows more about it than I do. Thnaks for all the help!!

(quoted from post at 23:06:52 06/29/17) TRied to fix alternator problem today. Checked a lot of the things that were suggested. Put new alt on and with out hooking the 1 or 2 posts as suggested., just hooked up output wire. When I started the engine it pegged the amp gauge to the charge side. Shut it down immediately. Going to get someone that knows more about it than I do. Thnaks for all the help!!

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WILL TELL YOU THAT DEPENDING ON WHAT REGULATOR VERSION IS USED IN THOSE dELCO 10-si ALTERNATORS, THEY WILL OUTPUT full BORE OR THEY WILL OUTPUT NOTHING.