alternator question

Ellis Kinney · Sep 25, 2020

Farmall M tractor converted to 12 volt, neg. ground, electronic ignition with an alternator. NORMALLY when I start the tractor it shows discharge at first. I let it warm up for a minute and add a touch of throttle and it starts charging. It has quit doing that. What do I do to check the alternator?? Thanks, Ellis

caterpillar guy · Sep 25, 2020

Put a volt meter across the battery posts or read off the battery terminal on the alternator . Should read around 13-15 volt. More will boil battery and less is not charging enough. 13.5-14.5 is optimal.

old · Sep 25, 2020

What brand and type of alternator do you have?? Sounds like a normal 1 wire and how they act which is not a real good set up

Janicholson · Sep 25, 2020

Before the volt meter, look at the belt tension. Pushing hard with your thumb in the center of the open span, should deflect about 1/2" max, 3/8 minimum.
Another quick check is to use a hacksaw blade and (carefully) put it against the bearing on the back of the alternator. If it tugs firmly on the blade, it is getting exciter voltage, and the rotor is magnetized. Jim

Billy Shafer · Sep 25, 2020

A volt meter would be the best way to find out. Real easy to do.

Fred Jones · Sep 25, 2020

Mine does that same thing. You have to get a few rpm's from idle to exite the alternator before it starts charging and it charges fine.

Olfolks · Sep 25, 2020

a good repair shop should be able to put a low RPM exciter in it for you. The local alt. repair guy near me made a 6v pos ground low RPM 1 wire for me to put on a 720 JD diesel

Steve@Advance · Sep 25, 2020

Is this a 1 wire 10SI Delco?

If so there should be battery voltage at the output wire at all times.

If a 3 wire Delco 10SI, there should be battery voltage at the output stud, and at the #2 spade terminal at all times, and voltage at the #1 spade terminal with the ignition on.

If all this checks good, and the belt is tight, suspect there is a problem with the alternator.

As you say, it does require a bit of throttle to initiate the charge on start up. But once charging it should continue to show some charge when returned to idle.

chas036 · Sep 25, 2020

Those one wire alternators usually don't kick in until a certain rpm is reached. Now since you probably are not seeing nothing , you probably burned out the internal voltage regulator.

JMOR · Sep 25, 2020

(quoted from post at 13:57:39 09/25/20) Those one wire alternators usually don't kick in until a certain rpm is reached. Now since you probably are not seeing nothing , you probably burned out the internal voltage regulator.

hat is an easy check! Small screw driver in "D"-hole & it should give full output.

alternator question

Ellis Kinney

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caterpillar guy

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old

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Janicholson

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Billy Shafer

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Fred Jones

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Olfolks

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Steve@Advance

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chas036

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JMOR

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