Need Advice on Amp Meter w/Alternator reading

[Mark Maron]

Hi everyone and thanks in advance on this topic:
MY CAR:


NEW wiring Harness from Tyree (perfect)
Original 20/20 Amp
Set Point alternator
960 Miles on the car
Did a complete engine overhaul, rings, valves everything and engine running fine.
“B” Carb
“B” Distributor

Started the car last night to drive home, approx. an hour drive and 30 miles, and tapped the accelerator to kick in the alternator, began to drive and noticed when the lights were turned on I got a discharge and then went back to “0”.. drove home but also noticed that the amp was fluctuating when i slowed down to a discharge of -10. Drive and comes back to “0”.. Then later when Im almost home i notice when i drive the amp discharges as driving to again -10, light dim an then bounces back to 0 lights get bright again, and then the bounce back to discharge of -10 and back to 0 again……this was the last 8 mile drive that i dealt with. Car never died out, came close i have my idle set low with the timing. Then pulled into the garage. and sat for a bit.. car was on discharge -10, then the bounce back and then i killed the headlight. BAM went right back to “0” and stayed that way for good, yes it dropped slight when i hit the brakes but nothing to even note.

…..is this normal with an alternator…..or what is the issue. Do i have the wrong AMP Meter as it has been suggested that i should be using a 30/30 with an Alternator NOT the 20/20. OR what are your thoughts..I was under the impression all these years that what is happening is NORMAL for an AMP with a GENERATOR, BUT not an Alternator!! Has me frustrated on this...:sad


Looking for your suggestion and advise

Mark

[Mitch]

Personally i always do my testing with a voltmeter hooked to the battery. This way i know exactly what is what with a load, without a load etc:

[tbirdtbird]

Mark,
not sure what you mean by a 'set point alternator'
It sounds like the type of regulator (which is internal to the alternator) used is the one-wire type which needs to be revved up to excite the field and wake it up.
It sounds like that regulator is faulty.
I seriously doubt it has anything to do with the scale on the ammeter.

I used to be a fan of the one-wire alternators because they are so easy to set up.
They give trouble, tho, because there are no longer ANY American made regulators of this type. Thus, you know where they are made, and they don't hold up.

If you are a 12V system I can give you a PN from O'Reilly's for a lifetime guaranteed alternator, of the 3-wire type.
It is actually very easy to wire these, you would use your existing wiring and add a small jumper right at the alternator, and add a diode to the wire going to your ammeter.

I can walk you thru the whole thing if that will help. But please recall my assumption here is that you have now a so-called one-wire alternator.

Once I switched to the 3-wire alternator, which we actually make into a 1-wire as I mentioned, all my reliability problems went away.
Dave

[Mark Maron]

Mark,
not sure what you mean by a 'set point alternator'
It sounds like the type of regulator (which is internal to the alternator) used is the one-wire type which needs to be revved up to excite the field and wake it up.
It sounds like that regulator is faulty.
I seriously doubt it has anything to do with the scale on the ammeter.

I used to be a fan of the one-wire alternators because they are so easy to set up.
They give trouble, tho, because there are no longer ANY American made regulators of this type. Thus, you know where they are made, and they don't hold up.

If you are a 12V system I can give you a PN from O'Reilly's for a lifetime guaranteed alternator, of the 3-wire type.
It is actually very easy to wire these, you would use your existing wiring and add a small jumper right at the alternator, and add a diode to the wire going to your ammeter.

I can walk you thru the whole thing if that will help. But please recall my assumption here is that you have now a so-called one-wire alternator.

Once I switched to the 3-wire alternator, which we actually make into a 1-wire as I mentioned, all my reliability problems went away.
Dave

OK no I have a 6 volt system Mitch. I get my alternators from here and always have been perfect....take a look...

http://www.buckeyeautoelectric.com/model-a/model-a-alternators/

Set point means it won't go above the 50 amps and burn out that is all, but this is what i use and many club members. I have a NU-REX sitting around also at home.

[Mitch]

""OK no I have a 6 volt system Mitch""

???? You can still use a voltmeter to test 6V

[1931 Flamingo]

I'm running an alt (6V) also, after getting it to fire I have a steady output, dips when I use the signals and/or brakes. Hovers around 0 with the lights on. I do have a 30 amp ammeter but it never produces anywhere near that. I'm thinking it's your alt. Try swapping in the Nu-Rex. Easy enough to do.

Paul in CT

[Mark Maron]

I'm running an alt (6V) also, after getting it to fire I have a steady output, dips when I use the signals and/or brakes. Hovers around 0 with the lights on. I do have a 30 amp ammeter but it never produces anywhere near that. I'm thinking it's your alt. Try swapping in the Nu-Rex. Easy enough to do.

Paul in CT

thanks Paul...seem to be leaning that way also......

[tbirdtbird]

agree. it seems to be the alternator.

not sure i understand the need to limit the output of an alternator. It only puts out what you need. (they are self-regulated) There is no way a Model A could ever demand more than about 30 amps of current, even with the AC we run here in Texas. Would love more info on that, but get your immediate problem fixed first!

[Tom Wesenberg]

You can connect a volt meter from the battery post (hot side) to the alternator output stud, then turn the lights on and check for voltage loss. You should have less than one volt. Then reverse the volt meter leads, turn the lights off and start the engine to see if you have any loss while the engine is charging the battery.

It sounds like a bad voltage regulator or poor connection in the charging circuit.

If you have the small pulley, be sure the belt isn't slipping.

[Mark Maron]

meaning Tom the alternator as mentioned in this feed??

[DaWizard]

Also, to keep from having problems, I would remove the alternator and scrape the paint off the engine mounting surface to make sure you have a good ground!

[Mark Maron]

UPDATE: Well it did after a lot of volt testing with Mitch,..THANK YOU!! turn out to be the Alternator. There was NO charge coming from it at all to the battery with a 1500 rpm read and the
light on...stayed at 6.2 all the time, changed to a NU-REX super high output i had and now here is the reading....charging and took for a ride with lights on an never dropped. Thanks all who helped me here on this....INCREDIBLE FORUM!!!




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