Alternator started sparking

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Are you trying to track down a .3v voltage drop?

Maybe your meter is not accurate?

Yeah. When the blue ignition wire is connected it drops .3 at the battery and then an additional .2 at the alternator. When it’s not connected, the readings go back up, with the alternator and battery showing the same numbers, without the drops. When the car is running the gauge jumps to over charging and then settles. The alternator is putting out between 14.8 and 15.3 and is not steady. I’ve run a direct power wire from alternator, bypassing the voltage regulator, to the battery for a short time and there wasn’t any voltage drops and the alternator put out around 14.2, steadily.
 
The drop causing this has got to be more than .3V somehow. The drop matches the amount of overvoltage. Another way to check is to check what v the VR is regulating at. To do that measure between the VR mounting ear and the VR IGN terminal "as close as you can get." (This is with engine running fast idle and battery normalized, engine bay/ engine/ battery warm. Once again, this is usually at the ballast. If it measures say, 13.8 at the ballast, and the battery is running 14.8 then you have a 1v drop in the harness and ground system combined

HOW DOES this work?

The VR only "knows" one thing and that is to provide field current up or down until system regulation point is "met." So the VR ramps up field current until it's IGN terminal (also the sensing point on these VR's) --until that point is at the VR setpoint. This is nominally 13.8--14.2 with VR warm.

But what is HAPPENING (assuming the VR is regulating correctly) the VR, because of the drop, must ramp system voltage AT THE BATTERY higher so that as the "drop" happens through the system, harness, and to the VR IGN terminal, the battery must be higher to compensate for the drop

BEAR IN MIND that in a common drop condition where the drop is "let's say" in the bulkhead terminal or ignition switch/ connector in the "IGN1/ run" line. there are various loads on that line. Depending on year, 70/ later they are
ignition system, whatever that might be
VR operating circuits
Field current through the alternator field
Electric choke if used
Various smog devices if used

Not all these loads are drawing the same current with engine on or off or various RPM, and if you disconnect anything during the troubleshoot, the current and drop through that line will change / lesson

The easy way out is a relay
 
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The drop causing this has got to be more than .3V somehow. The drop matches the amount of overvoltage. Another way to check is to check what v the VR is regulating at. To do that measure between the VR mounting ear and the VR IGN terminal "as close as you can get." (This is with engine running fast idle and battery normalized, engine bay/ engine/ battery warm. Once again, this is usually at the ballast. If it measures say, 13.8 at the ballast, and the battery is running 14.8 then you have a 1v drop in the harness and ground system combined

HOW DOES this work?

The VR only "knows" one thing and that is to provide field current up or down until system regulation point is "met." So the VR ramps up field current until it's IGN terminal (also the sensing point on these VR's) --until that point is at the VR setpoint. This is nominally 13.8--14.2 with VR warm.

But what is HAPPENING (assuming the VR is regulating correctly) the VR, because of the drop, must ramp system voltage AT THE BATTERY higher so that as the "drop" happens through the system, harness, and to the VR IGN terminal, the battery must be higher to compensate for the drop

BEAR IN MIND that in a common drop condition where the drop is "let's say" in the bulkhead terminal or ignition switch/ connector in the "IGN1/ run" line. there are various loads on that line. Depending on year, 70/ later they are
ignition system, whatever that might be
VR operating circuits
Field current through the alternator field
Electric choke if used
Various smog devices if used

Not all these loads are drawing the same current with engine on or off or various RPM, and if you disconnect anything during the troubleshoot, the current and drop through that line will change / lesson

The easy way out is a relay

Thank you! I’ll have time Monday to get it done. I appreciate the help!
 
The relay worked for the most part. It’s charging at a constant 14.2 and no drop between the alternator and battery. When I put on my headlights though, there’s a sizable overall amp drop and there’s an additional drop from alternator to battery of .30. It’s a great step. I only had an hour to mess around tonight, but tomorrow I’ll have the whole day to work on it. The front marker light is out and I’m assuming it’s the cause. I’ll find out tomorrow. Thanks again y’all!
 
Front headlights on.

3E287122-D1EE-4A1E-9E28-9EDE9941A457.jpeg
 
After trying to figure out the voltage drop when I turned my lights on, my alternator is now only putting out 12.4, basically matching my batteries power. The only thing I did was bypass the 3 prong connector for the front marker light. The connector was old and brittle, so I clipped the wires and connected them directly. That’s the only change I made. While searching for possible issues, I changed out an old fusible link. Nothing changed. I started looking for possible issues and ended up finding out that when I use my brake pedal for a ground, I get a 1.7 volt drop, compared to every other place I ground on. I don’t f’n get it.
 
THANK YOU GUYS!!! It finally happened, my electrical system is sorted out. Man, I feel like a huge burdens taken off my shoulders. I learned a ton from your advice here and responses to posts from 67Dart273 and Mattax. I thank y’all enough! I’m done learning for a while. Well, tomorrow I’m swapping in an 8 3/4 rear... We’ll see how it goes. I’m looking forward to mechanical work. I’m hoping it’s a choice next time I’m sorting out my electrical. Lol.
 
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