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Amp gauge bouncing between discharge and charge at idle

440 PHIXX

The Island of Misfit Mopars
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I put a new rebuild alternator in my ‘68 Satellite 383, and regulator. At idle the amp gauge is going back and forth between charge and discharge. Lights are following the gauge bright to dim. At higher RPM’s it acts normal. USA regulator, GM Chinese rebuilt alternator. Any ideas what would cause that? I checked to make sure all connections were tight. This just started btw. It was fine for a month.
 
Make sure everything is grounded, sounds like a regulator problem. have you tested with another amp meter?
 
Make sure everything is grounded, sounds like a regulator problem. have you tested with another amp meter?
It’s only happening when it’s running. Like normal it just goes to discharge when lights are put on and the engine is off. I guess it could be the amp gauge going bad. I’ll check the grounds again. I did check them after I installed the rebuilt alternator. The regulator went bad after that so I put a new one in as well. I may just put another alternator in it.
 
I think I’ll look thru my parts stash, and try a different regulator first. It’s the easiest thing to swap out. :D
 
What I’ve never seen in all the years I worked on theses old Mopars is the amp gauge going between D and C wildly like that. It’s swinging what is probably 30 amps each way.
 
I put a new rebuild alternator in my ‘68 Satellite 383, and regulator. At idle the amp gauge is going back and forth between charge and discharge. Lights are following the gauge bright to dim. At higher RPM’s it acts normal. USA regulator, GM Chinese rebuilt alternator. Any ideas what would cause that? I checked to make sure all connections were tight. This just started btw. It was fine for a month.
My guess at what the problem is: GM Chinese rebuilt alternator......why not a USA Rebuilt '68 Mopar round back alternator and new electronic regulator to replace the origional mechanical voltage regulator.
BOB RENTON
 
My guess at what the problem is: GM Chinese rebuilt alternator......why not a USA Rebuilt '68 Mopar round back alternator and new electronic regulator to replace the origional mechanical voltage regulator.
BOB RENTON
It wouldn’t surprise me. I’m seeing many on YT and other forums complaining about an up to 50% fail rate on Chinese parts in the last year. I do still have my original that came off the car. Worked for 54 years. I did use a USA regulator, the points type. It wasn’t rated for 60 amps. So I ordered the 60 amp model. It’s gotta be one or the other. Probably both. I blame the 383 for me not going to electronic regulator. It’s so damn easy to check and change the points on it, that I never put electronic ignition on it. The last time I did that on a 273, I changed to an electronic regulator with the 4 pin box.
 
1st Question..
What is the idle RPM speed?
If too low, then the alternator is not spinning enough to generate enough output voltage and the regulator is cutting in/out.. As RJRENTON correctly recommended...
Time for an upgraded higher current output alternator and electronic voltage regulator..

Just my $0.02...
 
Before you do anything check with volt meter and check grounds.
Sarcasticly saying......with the wild ammeter fluctuations (from negative to positive readings), be on the lookout for the ammeter to burst into flames or to melt down taking associated wiring connections as well......wildly fluctuating ammeters are not to be trusted......ooopps....wrong thread.....
The REAL QUESTION IS: WHY would the OP choose a rebuilt GM style altetnator (of Chinese? origin), in lieu of Mopar? Beside mounting and alignment issues, the early GM units used a external mechanical voltage regulator, Model 10 and later MODEL 12 units and ultimately the 10 SI and 12
SI, WITH SI meaning SYSTEM INTEGRAL (built in regulator using the internal diode trio and regulator for rotor power source and output voltage regulation). A Mopar to Mopar alternator replacement is a, in popular vernacular, a "no brainer" decision. Why go looking for problems that don't need fixed. Unless, the auto parts counter person doesn't know the difference and just wants to make a sale. Just talking out loud......
BOB RENTON
 
Sarcasticly saying......with the wild ammeter fluctuations (from negative to positive readings), be on the lookout for the ammeter to burst into flames or to melt down taking associated wiring connections as well......wildly fluctuating ammeters are not to be trusted......ooopps....wrong thread.....
The REAL QUESTION IS: WHY would the OP choose a rebuilt GM style altetnator (of Chinese? origin), in lieu of Mopar? Beside mounting and alignment issues, the early GM units used a external mechanical voltage regulator, Model 10 and later MODEL 12 units and ultimately the 10 SI and 12
SI, WITH SI meaning SYSTEM INTEGRAL (built in regulator using the internal diode trio and regulator for rotor power source and output voltage regulation). A Mopar to Mopar alternator replacement is a, in popular vernacular, a "no brainer" decision. Why go looking for problems that don't need fixed. Unless, the auto parts counter person doesn't know the difference and just wants to make a sale. Just talking out loud......
BOB RENTON
I should have said AC Delco. I mistakenly said GM. It’s a Chrysler rebuilt, and a round back ‘69 and earlier style. I think it’s the voltage regulator. I ordered the 35 amp and the alternator is 60 amp.
A71751FD-13CF-46C6-B107-29F9E2316042.jpeg
 
1st Question..
What is the idle RPM speed?
If too low, then the alternator is not spinning enough to generate enough output voltage and the regulator is cutting in/out.. As RJRENTON correctly recommended...
Time for an upgraded higher current output alternator and electronic voltage regulator..

Just my $0.02...
It was working fine. It just started acting up. See pic above. Thanks for your help. Everyone. :thumbsup:
 
What is weird is that it only acts up at idle. It charges normally after about 1500 RPM. It worked fine for a month.
 
I should have said AC Delco. I mistakenly said GM. It’s a Chrysler rebuilt, and a round back ‘69 and earlier style. I think it’s the voltage regulator. I ordered the 35 amp and the alternator is 60 amp.View attachment 1342315
The VOLTAGE REGULATOR has nothing to do with the output amperage of the alternator. The regulator's sole function is o control the system voltage by controlling the alternator's field voltage resulting in a steady state output voltage. The alternators CURRENT output is determined by the diodes and the stator windings and wire size and is design limited by the IMPEDANCE OF THE STATOR WINDINGS (AC resistance).
Just thought you might like to know......
BOB RENTON
 
The VOLTAGE REGULATOR has nothing to do with the output amperage of the alternator. The regulator's sole function is o control the system voltage by controlling the alternator's field voltage resulting in a steady state output voltage. The alternators CURRENT output is determined by the diodes and the stator windings and wire size and is design limited by the IMPEDANCE OF THE STATOR WINDINGS (AC resistance).
Just thought you might like to know......
BOB RENTON
I burned out the Wells one that came with the car a week after installing the new alternator. I put the 35 amp one I just bought and it seemed to allow the alternator full field for the first five seconds after I start the car. I ordered the 60 amp one and a different alternator that has a single pulley.
7D8EF185-394C-4CA9-96BC-483651CA03FE.jpeg

I had the VR101 in there. I still can’t figure out why it only does it at idle. It’s the whole electrical system. All the lights are flickering with the amp gauge.
 
Last edited:
I burned out the Wells one that came with the car a week after installing the new alternator. I put the 35 amp one I just bought and it seemed to allow the alternator full field for the first five seconds after I start the car. I ordered the 60 amp one and a different alternator that has a single pulley.View attachment 1342421
I had the VR101 in there. I still can’t figure out why it only does it at idle. It’s the whole electrical system. All the lights are flickering with the amp gauge.
The single field wire alternator and the origional mechanical voltage regulator operates by adjusting the alternator's field voltage by:
1. Applying full field voltage initially after starting by bypassing an internal dropping resistor under the device.
2. After car is running and system voltage is increasing, the points in the mechanical regulator poinrs open, inserting a resistance in the field voltage supply, reducing the alternator's field voltage and the overall system voltage to a nomimal 14.0 volts.
3. If the system voltage continues to increase, due to light electrical loads, the mechanical voltage regulator disconnects the field voltage and the alternator stops charging. This results in a DECREASE in system voltage which results in the mechanical voltage regulator reconnecting the alternator field voltage connection, thru the internal resistance, causing the alternator to resume charging at a reduced level.

The above sequence repeats constantly to try and maintain a NOMINAL system voltage of 14.0 volts (+/-). The continually moving contacts of the mechanical voltage regulator, over time will arc and ultimately fail. The ELECTRONIC version, uses a switching transistor to handle the on / off switching of the field voltage to the single field wire alternator. The total circuit adds temperature compensation and is more accurate than the mechanical version and the design is considered a "voltage sinking" and handles the inductive reactance of the rotating field voltage without harm.
IF, your mechanical voltage regulator is experiencing wild voltage swings (ammeter charge-discharge swings) IT IS DEFECTIVE......Replace it with the ELECTRONIC VERSION replacement. Just my opinion of course.
BOB RENTON
 
Update... I installed the $17 electronic Chinese regulator. It looks cheap compared to the Standard USA, but it’s working flawlessly. I should give it a few days before I declare success but, the other one from the start would swing the amp meter over quite a bit in startup. It even would make the alternator belt squeal. Anyway... hope it keeps going! Btw... this instance is when an amp gauge shows you what’s going on compared to a volt meter.
 
The mechanical one on my car was showing big swings in the gauge, so I got an electronic one off eBay. That one was a look alike that was right at home in my all stock engine bay. Amp gauge held steady as a rock and moved slowly back and forth. I also added a dedicated ground while I was at it, car was new to me and I do this on all of my cars going back decades. After 100 miles the new reg failed. Completely. So back on went the original and it’s been fine with the new ground in place.
 
My Chinese electronic one sent my car into full overcharge as soon as I plugged it in. I checked it’s ground and it was fine and it had 12.1V at the ign side of regulator so I grabbed a new mechanical type off rock auto and it’s dead nuts centered on the gauge charging beautiful and no flickering of any sort. Wish they made an electronic look alike in the USA so I could trust another but for now old tech works for me.
 
how about this adjustable style? Allows use of higher than stock alternator output and you can adjust it on the back while measuring voltage at idle. Prevents overcharging and frying gauges. After burning up a few of my gauges with an overcharge situation using a 70A powermaster alternator, I switched to this, dialed it in and it's been working flawlessly.

HD External Adjustable Voltage Regulator Chrysler Dodge Plymouth, 1970-87 | eBay
 
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