Alternator Pulsing

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jimmyray

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I have replaced my Alternator and Voltage regulator (AC Delco, the Best one Advance Auto has)

When the car is running, the Ammeter is steady sometimes, and other time is pulses, or blinks, on and off. This causes the interior light to flicker at the same rate.

I ran a wire direct from the alternator to the battery, and replaced the hotwire to the Voltage Regulator with a new one direct from the relay I am using to power the ignition.

I have cleaned the plug, and have 2 screws with star washer grounding the voltage regulator.

Thoughts?
 
Even though you're using a relay to power the regulator, actually check the regulator hot lead AND ground

Turn your ignition to "run" but engine not running. Stick one probe of your meter on the battery POS post, and the other on the regulator IGN terminal. You are hoping for a very low voltage, the lower the better, and not above .2V (2 tenths of a volt)

Then check the ground path. To do that, start the engine, run at "low to medium cruise" RPM, and check both with loads off and with lights, heater, etc on

This time, stick one probe on the battery NEG terminal, and the other directly onto the regulator mounting flange. Be sure to stab through any rust, dirt, paint, chrome, etc.

Once again, you are looking for a very low voltage the lower the better

Is this an old style electro--mechanical type or is it a replacement solid state? You can tell by looking at the bottom of the regulator. If there are two fairly heavy resistors under there, it's an electro/ mechanical type, and may be suspect

There is also some chance that you have an odd ground loop. You might try a heavier ground. If your battery is front mount, the main ground should already be to the block. You can add a very heavy ground by getting a 1 ft starter cable (ring to ring) and bolting it to the unused alternator mount holes on the rear of the driver side head. Ground the other end to the firewall, either big heavy bolt through firewall, or to such bolts as the master cylinder mounting studs.



Electro--mechanical, notice resistors

440-1621-large.jpg


Underside of a couple of solid state replacements, no resistors

80f4_35.JPG
 
Nope. None of that stuff.

My money: the regulator for the instrument cluster. Go solid state. I did all the same stuff to my car and that never got better. Replaced the IM regulator, and it's all rock-steady now.

I'm hoping and praying that you put a fusible link in your alternator-to-battery wire, too.
 
Sounds like your voltage regulator. Do your headlights, taillights also pulse? Did it do that BEFORE you replaced your alternator? If not, I would say your alternator might be the problem. Auto Zone and Advance Auto have been known to sell bad alternators, and I have gotten 3 bad ones in a row for the same vehicle.
 
all mopars built before 1973 surge when sitting at idel, after 73 they went to electronic ignition,,,and a constant charging system,,,and voltage regulator,,,

thats why when u convert a pre 1970 car to mopar electronic ignition u have to use that blue regulator,, or add a wire to the system and go to a constant regulator,,,
 
Duh me. I forgot to mention I put in a later style 2 field alternator, with the solid state voltage regulator.

I have the voltage regulator within 3 inches (on fenderwell next to alternator), wires aboout 4" and 6" long.
 
Nope. None of that stuff.

My money: the regulator for the instrument cluster. Go solid state. I did all the same stuff to my car and that never got better. Replaced the IM regulator, and it's all rock-steady now.

I'm hoping and praying that you put a fusible link in your alternator-to-battery wire, too.

Can you give me a lead on where to source such a thing?
 
Even though you're using a relay to power the regulator, actually check the regulator hot lead AND ground

Turn your ignition to "run" but engine not running. Stick one probe of your meter on the battery POS post, and the other on the regulator IGN terminal. You are hoping for a very low voltage, the lower the better, and not above .2V (2 tenths of a volt)

Then check the ground path. To do that, start the engine, run at "low to medium cruise" RPM, and check both with loads off and with lights, heater, etc on

This time, stick one probe on the battery NEG terminal, and the other directly onto the regulator mounting flange. Be sure to stab through any rust, dirt, paint, chrome, etc.

Once again, you are looking for a very low voltage the lower the better

Is this an old style electro--mechanical type or is it a replacement solid state? You can tell by looking at the bottom of the regulator. If there are two fairly heavy resistors under there, it's an electro/ mechanical type, and may be suspect

There is also some chance that you have an odd ground loop. You might try a heavier ground. If your battery is front mount, the main ground should already be to the block. You can add a very heavy ground by getting a 1 ft starter cable (ring to ring) and bolting it to the unused alternator mount holes on the rear of the driver side head. Ground the other end to the firewall, either big heavy bolt through firewall, or to such bolts as the master cylinder mounting studs.

Great diagnosis process, I will check these!
 
The mechanical voltage limiter may or may not be the problem. In most cases there isn't a simple way to diagnose it other than locate the wire that supplies 12 volts to it a clip the wire. It's dark blue with a white tracer and routed in the harness tape out from mian harness to the round harness connector that attaches to the instrument panel.
Snip the wire, pulse condition goes away, found the problem. Replace the limiter repair the sniped wire, happy moparing. Good luck
 
Nope. None of that stuff.

My money: the regulator for the instrument cluster. Go solid state. I did all the same stuff to my car and that never got better. Replaced the IM regulator, and it's all rock-steady now.

I'm hoping and praying that you put a fusible link in your alternator-to-battery wire, too.

I'd like to hear your theory on how the instrument regulator affects the ammeter
 
Duh me. I forgot to mention I put in a later style 2 field alternator, with the solid state voltage regulator.

I have the voltage regulator within 3 inches (on fenderwell next to alternator), wires aboout 4" and 6" long.

This could very well be a "poor ground" problem. It is imperative that the battery NEG and the regulator "see" the same ground.
 
I'd like to hear your theory on how the instrument regulator affects the ammeter

It is a pulsing draw on unfused 12 volts. How much draw is anyones guess.
Basicly the same way turn signals can cause the amp gauge needle to twitch.
 
Check the charging voltage at the battery KOER. Verify wether the voltage is fluctuating or not. Next have a ripple test done on the alternator. A ripple test checks A/C voltage leaking throught the rectifier(diodes). A bad diode can cause flickering lights.

(KOER means Key On Engine Running.)
 
NAPA, get a 14 gauge fusible link. If I recall, about three bucks.

Good to know. But I was actually referring to the solid state dash voltage regulator, and I was not clear on my question.

I removed the extra wire, as it did not help, and was a safety concern.
 
Great diagnostic advie all around. The motor has the ground strap from the battery to the drivers side iron cylinder head, whereas the ground strap from the motor to the firewall attaches to the aluminum intake manifold. While I doubt it matters, I will move the ground strap to the pass side cylinder head.

I will also check to see if it pulses at the alternator positive output stud.

It does not pulse all of the time, and can be loaded or unloaded. I noticed that when first started, the ammeter swings to high charge,, and as it backs down to closer to center, it begins the pulsing/switching behavior. It can be seen in the headlights (that are relay equipped) and in the dash and interior lights.
 
It is a pulsing draw on unfused 12 volts. How much draw is anyones guess.
Basicly the same way turn signals can cause the amp gauge needle to twitch.

Well here's the thing:

The instrument limiter is not hooked to the ammeter

The gauges don't draw very much current and the gauges is all the limiter supplies

Very VERY difficult for this old guy to believe.

My guess would go more like this:

One of you thought you found that trouble when in reality you wiggled the harness getting the cluster in/ out and wiggled the ammeter connections or the bulkhead connector, which had loose connections.
 
on my 70 dart i had a similar prob it mainly pulsed above idle .i am in the process of putting in a new wire harness[aftermarket].and i found two wires slightly melted together right at the inside side of the bulkhead connector.i am not even sure this is where my problem was but it seems very possible to me. i tried other alternators,regulators,and bypassing and could not find the problem otherwise. good luck
 
If it is just a little movement at low rpm, then it probably is just the voltage ripple.
 
An electronics engineer who designs voltage regulators told me that sometimes the alternator ripple frequency and regulator operating frequency can get close to each other and will cause voltage fluctuations. Electrosystems has changed the operating frequency of their regulators to 1000hz. to eliminate this problem. The bad news is, their regulators are certified for aircraft use and cost well over $100 dollars. I don't know if any other manufacturer has done this. I would try a different regulator and also find someone who checks alternators with an oscilloscope and see what the ripple pattern actually is and if all the diodes are carrying their share of the load.
 
checks alternators with an oscilloscope and see what the ripple pattern actually is and if all the diodes are carrying their share of the load.


Or just turn on your AM radio...................LOL
 
When installing my batt in trunk, along with other wiring going on at the same time; I found that the firewall ground is too small. Get a battery cable, bolt to head, and bolt to kframe. Keep the little tiny firewall wire. Or, I installed a bigger one. Problems solved, you can't have enough redundant grounds in a car.
 
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