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I check my charging voltage and it is closer to 14.9V which is higher than I'd like. I traced the voltage drop to the neg battery cable itself which read ~2.5 ohms.



That is ONE HELL of a lot of resistance if correct.

But don't try to shoot bad grounds and voltage drop with resistance, do so with voltage tests

Just picture in your mind the path that current takes. "th juice" going to the regulator comes off the battery, through the bulkhead and ammeter, through the ignition switch, harness, etc, back out the bulkhead and feeds to the regulator

There are a couple of places, there, namely the bulkhead connector, the ignition switch and the connector on the switch, that can create drop

Turn the key to "run" but with the engine not running

If you have breaker points ignition, make sure the points are closed, and make the test rapidly

Compare battery voltage to voltage feeding the regulator. On a 69 and earlier regulator check right at the regulator ignition terminal

On 70 and later this is harder. you can check at the blue field on the alternator. If you can get to the "key" side of the coil ballast, check there

What you are looking for here is the difference between battery and that point feeding the regulator. You want less, that is "zero" is perfect. If you come up with more than, say 3/10 of one volt, find out why.

Same with ground only this time, check with engine running fast enough to charge. Put your voltmeter on very low DC volts. Stick one lead to the battery NEG post. Stick the other lead to the regulator mounting, "the case." Here again, zero volts is perfect. Anything more than a 1/10 volt or so, you need to work on grounding.

Back to your neg cable. Here again, best way to check cables "bad" or not is under starting current loads. This is made easy with access to a "load tester." But you can "cheat" by just running the starter, ignition grounded. Check voltage across the cables during cranking.


The voltage from the battery leaves it on the negative side just like all batteries and returns through the positive side, the alternator charges from the alternator through the engine wiring harness to the bulkhead connector and then through the under dash wiring harness through the amp gauge and back through the same harness and then goes to the battery to keep it charged. Come on you guys, GET THE BASICS correct before intentionally or unintentionally misleading those that don't know D.C. current flow



you can take your two cents and you can go stick it somewhere

i simply IN SIMPLE TERMS described the CURRENT PATH. the PATH that the current takes, JUST ENOUGH of the description to ILLUSTRATE THE POINT which is the "direction" in which most people probably "think."

It matters not, oh engineering xpert, "which way" the current flows, and by the way, it wasn't all that long ago (in the 20's) when people believed there was "current" going from plus to minus.

I WAS ATTEMPTING TO ILLUSTRATE IN NOT TOO TECHNICAL TERMS how voltage drop occurs. The probability is, if someone is wondering what the drop is "doing" that they will be measuring and troubleshooting "from the positive end" of the system rather than the "ground" end. That is all I was trying to illustrate. THE WAY THAT VOLTAGE DROP HAPPENS

NOW I NOTICE that YOU the ENGINEERING XPERT "did not" attempt to illustrate anything helpful, anything factual, anything concrete. I notice that you made NO helpful contribution AT ALL.

You did not suggest, for example, that the voltage regulator must be held that is "grounded" very very close to the battery NEG and therefore to remove, clean, and retighten the VR mounting bolts. I notice you DID NOT suggest, as an example, to examine and to check the VR connector(s) and to be sure they are clean and tight. I further notice, as yet a further example, that you did not suggest how to functionally go through the checks for bulkhead, ignition switch, and it's related connector. I NOTICE that you did not SUGGEST ANY of this.

Don't you feel "helpful?"

"I'd bet money" I've been involved with things electrical and electronic longer than you. Statistically, it's "bettable."

Last edited by DDodger; 02/22/15 06:06 AM.