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Alternator over amping

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ReidS TN- NAA

09-13-2005 05:59:16

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I have just recently rebuilt my Jubilee and after getting him fired up and running I noticed that my 12 V alternator was overcharging - or at least pegging out my +/- 30 Amp 2 pole ammeter. Before I tore ol Henry down he would charge just fine..peg up to about 10-15 amps and go back closer to zero after 30-45 seconds. Now - when I start up the ammeter pegs out at +30 amps and pretty much stays there even after 4-5 minutes of driving around. The needle will come off +30 only at very low idle (600 rpm)and then only to maybe +25 amps. I am pretty certain that I have my wires correct. Will this cause damage to battery/alternator? The wires aren't getting hot. How can I verify my alternator is charging properly and most importantly do I need to try and fix it and how? Any help appreciated. Thanks in advance. Pictues at 11!!

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ReidS TN-NAA

09-13-2005 19:00:40

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Update - amps dropping in reply to ReidS TN- NAA, 09-13-2005 05:59:16

Thanks for all of the good advice. I checked battery with key switch off - 12.6 V. With tractor running seemed to be checking around 14V going between post on alt and ground on battery - readings were all over the place with digital VOM. All of the wiring checked OK and correct as Dell inidcated -this harness and alt were good before rebuild. I decided to run it for a while as I haven't run him much (5-10 minutes max)since initial cranking from complete rebuild. After running for a few minutes I noticed amp meter reading dropping and after about 15 minutes was down to 16 amps at idle. Should I carry on and see what happens or is the battery still charging? I did not check alt case to ground yet and it is a fresh paint job. Two things I should note - I did drain the battery pretty well (but not completely) trying to start engine (another story about dist weights)and did charge it on a slow 2/6 amp charger overnight about a week ago - battery seems to start engine well -couple of turns and we're running. Any further advice or comments appreciated.

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tim in pa

09-13-2005 08:44:06

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Re: Alternator over amping in reply to ReidS TN- NAA, 09-13-2005 05:59:16

reid, first stop running it except for some testing, or you'll be buying a new battery pronto! second, assuming it's the same alternator, and assuming the ammeter is good, after you eliminate a voltage problem, rules are if amps goes up means resistance went down. in other words the current was able to get to ground easier. this is likely a short somewhere. recommend you check your wiring again.

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souNdguy

09-13-2005 07:25:47

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Re: Alternator over amping in reply to ReidS TN- NAA, 09-13-2005 05:59:16

I'd check the votlage on the battery.. without it running.. 12.6 for a 'good' charged battery.. check specific gravity as well. then check charge votlage.. look for about 14ish max.

Check connections at #1 and #2 terminals if this is a 3 wire job. Also check charge lug terminal. for grins.. use an aligator clip wire/jumper cable from the alternator case to the battery ground.. On at least one occasion I have seen enough paint on a connection to make a bad ground reference for an alternator.

Check charge wire to make sure there are no shorts ( doubt it ).. but check anyway..

I'd let it charge for 10 minutes if all the other tests check out.. and expect to see the charge taper down.. if it doesn't.. there is a problem somewhere. Might be a bad ammeter.. that's rare.. the new ones are fairly bulletproof... for 9$ you can get a new one...

Past that.. I'd have to say that there is a reason that there is 30a flowing.. like bad battery even if it 'reads'/ checks out correctly...

Soundguy

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Dell (WA)

09-13-2005 07:19:33

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Re: Alternator over amping in reply to ReidS TN- NAA, 09-13-2005 05:59:16

Reid..... you write: "I am pretty certain that I have my wires correct"..... WRONGO!!!

Your description has every indication of yer alternator's "P2" (voltage sense) slip-on terminal NOT SENSING the alternators volts output. Sensed, should read about 14.7 volts, UN-SENSED will be about 17-volts. EXCESS volts will OVERCHARGE yer 12v battery as indicated by yer ampmeter; boil yer battery dry; warp and short-out yer battery plates; and KILL yer battery.

There are 2 slip-on terminals on side-end of the commonally used Delco 10SI alternator. "P1" is the l/h blade and is supposed to be connected to a "switched excite" ignition switch ON source thru an idiot-lite or other isolation scheme. "P2" is the r/h blade and is supposed to be connected to the BIG STUD output of the alternator with a short wire.

And while it is possible that yer alternators internal solid state voltage regulator has failed, (take it into an autoparts store for "free" checkout) based upon yer description, my money is on alternator MISS-WIRE..... ....Dell, the amazing mind-reader

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duey

09-13-2005 06:49:07

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Check the VOLTAGE. . . in reply to ReidS TN- NAA, 09-13-2005 05:59:16

VOLTAGE, guy, voltage. Read the output voltage. It is supposed to be app. 14.2 volts. Not 15 or 16... And yes, higher voltage will ruin the battery. If the voltage is at 14, you may well have a bad battery... they do go bad in time... and time marches on! Good Luck... duey

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Rick H. Ga.

09-13-2005 06:36:32

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Re: Alternator over amping in reply to ReidS TN- NAA, 09-13-2005 05:59:16

If my electrical theory is correct, amps is the amount of current being drawn in an electrical curcuit. Is it possible your battery is getting weak and pulling the hi amp draw? Is is possible your amp meter is reading incorrectly?

You can check the alternator output with a volt meter. It should not produce more than about 14 volts.

The amp meter on my Jubilee (12 V conversion) reads hi (30 +) on start up and quickly drops down to near 0.

High amp draw is usually an indication of an electrical short. I suppose if the alternator is overcharging, it would have the same effect.

I'm sure Dell will clarify it for us.

HTH. Rick

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Slugg O.

09-13-2005 08:21:58

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Re: Alternator over amping in reply to Rick H. Ga., 09-13-2005 06:36:32

Seems that most alternators are 50 amp or MORE and a 30 amp guage should easily peg with more than 30 passing through it.

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Dell (WA)

09-13-2005 12:09:53

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Re: Alternator over amping in reply to Slugg O., 09-13-2005 08:21:58

Sluggo..... ..you are only semi-correct. The N-Ampmeter is hooked up to measure the amps into & outta the battery, NOT the genny/alternator output. The amount of amps into the battery is dependant upon delta-volts of the genny/alternator output and the battery volts potential. The battery volts potential is a function of chemical reaction. Normal battery charge is generally in the 5-amp range (after re-charging from the HEAVY starter drain which usually only takes about 5-10 minutes to re-charge)..... ..respectfully, Dell

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dan Hill

09-16-2005 04:18:57

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Re: Alternator over amping in reply to Dell (WA), 09-13-2005 12:09:53

Any more than 5 amps makes battery gas and corrode every thing,I like my generator,5 amps is plenty for normal use.The old generator is rated at 17 amp max.30 amp steady will cook battery.

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