12 volt conversion issue

Scott Limbourne · Dec 1, 2011

I have a Super M that has been converted using a delco three wire. The voltage at the battery was 16-17 volts while running. I thought I had a bad regulator inside the alt so I replaced with new alt. Same issue. I had alt tested and it is good but why am I getting 16 - 17 volts in the charging system? Battery is at 12.7 when everything is off. I will boil the battery putting that many volts into it.

Bob M · Dec 1, 2011

Scott - Make sure you are getting full battery voltage to the #2 terminal at the alternator!

Reason: #2 is the "voltage sense" terminal for the internal regulator. If #2 does not see battery voltage the alternator output (voltage) will "run wild" and run to 16 - 17 volts.

Also what kind of meter are you using? An analog VOM or industrial grade DVM (like a Fluke) will give true readings. A bargain DVM however can yield erroneously high readings on account of electrical noise present in the alternator output.

Scott Limbourne · Dec 1, 2011

I will check term 2 Bob. I am using a generic volt meter, I have a fluke too but the two meters I had handy seem to be the same. I will try the good meter.

See my thread in the first forum, see if you can get more info from there.

Brownie 450 · Dec 2, 2011

Bob, as usual is right about the sense terminal. I run a # 14 wire back to the heavy battery terminal on the solenoid from the sense terminal when converting to a Delco. This way, the sense terminal reads true battery voltage.

old · Dec 2, 2011

If the meter you used read 12.3 volts at the battery then 16 or so with it running then your meter is mist likely reading close enough for what your doing. You did not unhook a battery cable when you did the voltage test did you???? Reason I ask that is that is a good way to fry an alternator and also it would make an alternator put out max in doing so but I do not think you did unhook it but asked any how

Scott Limbourne · Dec 2, 2011

No the battery cables were connected.

old · Dec 2, 2011

I figured they where but it is and has been said to many times that you can test a charging system by pulling off one battery cable to doing that is both unsafe for the person and the alternator and could cost you $$ or even your life

Jon Hagen · Dec 3, 2011

Bob M may have it right, electrical noise on an old point type ignition system will make a DVM read high.
I saw that last summer while checking battery voltage on my Moline Big Mo 400 with stock point type ignition and 3 wire delco.

I checked charging voltage at the battery posts and was getting a very high and eratic reading with a digital volt meter, 17 +.
That did not seem possible, as the ammeter reading was only about 5 amps at high rpm.I got my little chepo 50 amp battery load tester
with the big analog voltmeter and connected it to the battery posts. It read a correct 14.5 volts. With the engine shut down, the DVM read the correct 12.6 volts, but aparently could not handle the noisy voltage signal from a running spark ignition tractor.

12 volt conversion issue

Scott Limbourne

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Bob M

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Scott Limbourne

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Brownie 450

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old

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Scott Limbourne

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old

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Jon Hagen

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