Alternator surging

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Will_H#24

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After replacing the voltage regulator a few days ago, this morning on a cold start the alternator gauge started surging. What is causing this?
 
If your alternator has two small gauge wires, then in 69, it should have had an electro mechanical regulator. Those have points in them, which play a lil tune on the dash gauge, which is normal until the battery comes up to charge. Eventually with a fully charged battery, they settle down.

If your alternator has only ONE small gauge wire on it, then it should be matched to go with an electronic regulator. These guys switch so fast between charge and discharge that you cannot really see the flicker on the sloooow Mopar gauges.

However a two wire alternator, can be converted to a one-wire just by grounding either brush, and then you can run an electronic regulator.
But you cannot go the other way, obviously, without taking it apart and modifying it.

If your electro-mechanical regulator never settles down, that is reason to suspect a problem.
 
mine does it
mine has done it for 20 years. i have investigated the hell out of it and have come to the conclusion its just like that....

just depends on how charged the battery is and how much load the car puts on the alternator.
if i stick the fan on or the headlights it stops
then after a while it stops anyway as the battery is up to full charge again.

mine will sometime ping between + and - for half an hour into a drive and then settle

mine had a points based regulator it now has an electronic regulator and the symptom is much the same battery charge level on a knife edge between being just enough or not enough.

more likely with a hugely over specified battery and a standard 36 - 60 amp alternator.
My battery same size and config as standard, fits the tray not too tall, but i just purchased one with cranking amps good enough to start a diesel truck.... unknown brand so went for overkill at low $$$ cost been in there 5 + years

can take quite a while to catch a huge battery up after it has been allowed to discharge to a level that is low but due to its size still allows the car to start easily

bog standard battery less capacity easier to charge up so the period of gauge wobble is less

this comes down to the way a battery charges

constant current 30+ amps with little voltage gain 12 v
constant current with voltage gain 25 amps 12.5 v
reducing current for little voltage gain 3 amps 13.9 v
constant voltage with near zero current to top it off 1 amp 14.5 V

somewhere in the 12 - 13 volt region if its still sinking current, you get gauge wiggle
 
Dave999 said:
mine does it
mine has done it for 20 years. i have investigated the hell out of it and have come to the conclusion its just like that....

just depends on how charged the battery is and how much load the car puts on the alternator.
if i stick the fan on or the headlights it stops
then after a while it stops anyway as the battery is up to full charge again.

mine will sometime ping between + and - for half an hour into a drive and then settle

mine had a points based regulator it now has an electronic regulator and the symptom is much the same battery charge level on a knife edge between being just enough or not enough.

more likely with a hugely over specified battery and a standard 36 - 60 amp alternator.
My battery same size and config as standard, fits the tray not too tall, but i just purchased one with cranking amps good enough to start a diesel truck.... unknown brand so went for overkill at low $$$ cost been in there 5 + years

can take quite a while to catch a huge battery up after it has been allowed to discharge to a level that is low but due to its size still allows the car to start easily

bog standard battery less capacity easier to charge up so the period of gauge wobble is less

this comes down to the way a battery charges

constant current 30+ amps with little voltage gain 12 v
constant current with voltage gain 25 amps 12.5 v
reducing current for little voltage gain 3 amps 13.9 v
constant voltage with near zero current to top it off 1 amp 14.5 V

somewhere in the 12 - 13 volt region if its still sinking current, you get gauge wiggle
Click to expand...
Thanks so much for your reply. The car has sat a few days so maybe that's it.
 
Will_H#24 said:
Did that help in your troubleshooting??
Click to expand...
Well i would make sure the reg has a real good ground then i would check all the connections for leaks and corrison then i would clean the bulkhead connector just to start .
 
Will_H#24 said:
Because the alternator was not charging the battery
Click to expand...
But it is charging now with the new VR?

can you take a video of the fluctuation.

If you can't post the video directly here you can most likely create a link that you can post
 
Dana67Dart said:
But it is charging now with the new VR?

can you take a video of the fluctuation.

If you can't post the video directly here you can most likely create a link that you can post
Click to expand...
It is charging now and I did try to upload a video but it's not allowed. Suggestions for an upload site?
 
Electrical is voodoo to me but I would be checking all connections, and make sure voltage regulator case has good ground. Both my ecu (elec.ign) and voltage reg run dedicated grounds direct to battery.
 
Looking at your you tube video ..

I say that is normal at a lumpy idle.

Get the RPM up to about 1000 to 1500 does it stop dancing?
 
Also the stock alt pulley is in the 2.5" diameter, rebuilds tend to u hise closer to 3 or larger.

The alt needs to spin (it's shaft speed) around 2000 to 3000 rpm 6.5 crank to 2.5 alt

700 engine RPM x 2.6 (6.5/2.5) = 1820, that is the low-end of good charging alt RPM.

700 engine RPM x 2.2 (6.5/3) = 1516, that is below the good charging alt RPM.

My 67, just started and got it off fast idle my pulley is closer to 2.5", I have a grounded field round back, and an electronic version of the electro mechanical VR.

New video by Dana Nance
 
Ammeters will reflect an undercharged battery by surging sometimes like that or burying the needle to the right. After a few minutes of driving or run time, they will normally level out toward the center.
 
Defective diode in the alt. As rpms increase, the time interval between the occurrence decreases & gives the impression that it 'has smoothed out'...
 
@Will_H#24

Did you notice that the motion of the gauge corresponds to the sound of your idle.

And it looks like the video I posted

Unless it does not flatten out at around 1500 to 2000 engine RPM it's normal.
 
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