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Old 12-18-2020, 11:36 AM   #1
rfitzpatrick
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Default Alternator Hasn't Kick In

Is the alternator still providing curcuit power even tho the amp gauge don't indicate? That is, am I on battery power alone until then?
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Old 12-18-2020, 01:10 PM   #2
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Default Re: Alternator Hasn't Kick In

Not all alternators perform the same way. Lets assumeyou have a GM -1 wire, which is probably the most common adaption. Some will not even kick in and produce electricity until your engine reaches about 1000 rpm. Some kick in at idle (about 600 rpm). Others cycle in and out.
The igniton circuit of the Model A (6 or 12 volt) only uses 1 to 2, maybe 3 amps. The needle will barely wiggle, which is hard to read on the amp gauges.
Check it this way. Start engine. Rev up to 1000 rpm or more - momentary. Watch needle - see if it wiggles.= when the alternator engages. If it does not move turn on the headlights and watch needle. It should move to discharge- about 10 amps and them move slowly back to 0 amps.

If it stays at 10 discharge, alternator is prolly not working. If it moves back to 0 then alternator is recharging the battery.


Clear as mud?????
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Old 12-18-2020, 01:19 PM   #3
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Default Re: Alternator Hasn't Kick In

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Originally Posted by rfitzpatrick View Post
Is the alternator still providing curcuit power even tho the amp gauge don't indicate? That is, am I on battery power alone until then?
Thanks
You don't mention but has it been sitting for a while with no battery connected? If so you may have to manually 'excite' the alternator the first time.

Here is a good YouTube Video on how to do that. We just had to do this on an alternator that has been sitting on the self for a couple of years. https://youtu.be/QPl7CTb685I
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Old 12-18-2020, 02:42 PM   #4
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Default Re: Alternator Hasn't Kick In

My A will run a long time on the battery alone as I have a red top battery. My alternator acted the same as yours and I took it to an alternator shop and they said it wasn't working at all. Regular car parts stores wouldn't even look at it because of 6V, positive ground. As Ken said, if you turn on the lights and get no response on the amp gauge other than minus reading (at fast engine rpm), chances are alternator is bad. The GM one wires are very finnicky about exciting a charge. After repair, mine will never excite at idle and lights or horn won't seem to excite a charge either. Only a few revs work, and then it stays charging until motor is turned off.
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Old 12-18-2020, 03:09 PM   #5
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Default Re: Alternator Hasn't Kick In

My alternator is self exciting so you have to rev the car to start it charging.
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Old 12-18-2020, 03:59 PM   #6
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Default Re: Alternator Hasn't Kick In

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Only a few weeks ago, I had to have my GM one wire alternator sorted out. The fields weren't exciting (neither was the fact that it wasn't working!). While the autoelectrician was in there, I asked him to replace the bearings etc so I end up with one probably better than new.
These alternators like quite a lot of revs to start charging. What size is the pulley on it? About 2" is normal - smaller than for a generator.
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Old 12-18-2020, 06:15 PM   #7
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Default Re: Alternator Hasn't Kick In

OK, usually, after just a short drive, and when I'm going thru the gears after a stop, the alternator would kick. It would allways show a charge afterwards. It's just that after 10 miles today, it never kicked so I was wondering about that. It's a Nu-Rex single wire. I've no starting issue, and our weather is rather cool (for Fla). The battery is about 3 months.
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Old 12-18-2020, 08:10 PM   #8
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Default Re: Alternator Hasn't Kick In

Install a volt meter. My car will indicate 14 volts with no reading on the ammeter because the battery is charged. The volt meter will tell you if the battery is OK after the car sits for a while before you even start the engine. Before the volt meter comes in the mail, measure the battery voltage with your multi meter after starting the engine and giving it a little bump to about 1,000 rpm. You can measure the battery voltage at the starter post.

You can buy a smaller alternator pulley so that the alternator starts to output at a lower rpm.
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Old 12-19-2020, 11:24 AM   #9
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Default Re: Alternator Hasn't Kick In

6 volt? 12 volt? Positive or negative ground?
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Last edited by katy; 12-19-2020 at 11:24 AM. Reason: Addition
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Old 12-19-2020, 04:11 PM   #10
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Default Re: Alternator Hasn't Kick In

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6 volt? 12 volt? Positive or negative ground?



6 Volt/Positive Ground
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Old 12-21-2020, 09:07 AM   #11
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Default Re: Alternator Hasn't Kick In

The single wire GM SI Series alternator may not be self exciting, so it will not produce current to run the Model "A" electrical system. Inside of the alternator there is a stator, and it must have some residual magnetism to start the alternator. Revving the engine may provide the starting magnetism, but there is a way to make the SI alternator start immediately.

Watch this video and pay attention to his discussion of the SI Series alternator.
https://www.youtube.com/watch?v=QPl7CTb685I
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Old 12-21-2020, 09:59 AM   #12
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Default Re: Alternator Hasn't Kick In

This is the perfect reason to buy a good quality volt/ohm meter. (DVOM or VOM) In this situation you can just put the meter across the battery and check voltage with engine off, with engine idling, and with engine revving somewhat. You'll be able to see exactly what's happening. "Needle wiggling" is a poor replacement for actual testing. If you like to get good service life out of your battery, and don't like being stranded, you NEED to know how well your charging system is operating.
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Old 12-21-2020, 10:35 AM   #13
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Default Re: Alternator Hasn't Kick In

It could be something simple like the belt is slipping, one of the tests I do to see if the alternator belt is slipping is to push on the alternator fan with a finger, if I can make the pulley slip on the belt with one finger I know the alternator won't be able to make near it's rated amperage or keep the battery properly charged
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Old 12-21-2020, 11:08 AM   #14
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Default Re: Alternator Hasn't Kick In

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Originally Posted by Bob Bidonde View Post
The single wire GM SI Series alternator may not be self exciting, so it will not produce current to run the Model "A" electrical system. Inside of the alternator there is a stator, and it must have some residual magnetism to start the alternator. Revving the engine may provide the starting magnetism, but there is a way to make the SI alternator start immediately.

Watch this video and pay attention to his discussion of the SI Series alternator.
https://www.youtube.com/watch?v=QPl7CTb685I
Isn't that the same You Tube video mentioned in post #3?
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