Call to all alternator experts & voltage gremlin hunters

[hughc]

"Get some Deoxit D5 and emory paper to clean contacts and grounds"

Tim, I don't want to take away from your post but for what it's worth I thought I should mention that a packet of flexible finger nail files is handy to have in your tool kit. They're stiffer than emory paper, can be shaped for hard to get at locations and your significant other probably always has a supply.

hughc

[bigel]

Originally Posted by mysocal911

Why do you continue to focus on just the ground lead? Doesn't the alternator connect to the
battery with another cable too?

Hey Dave,

My intention is not to frustrate you...I’m simply trying to run through the checks that I have found on the forum and those that members suggested in answering my call for assistance.

If you have something constructive to contribute, I’m all ears.

[mysocal911]

Originally Posted by mysocal911

As mentioned up-thread, marginal cable connections, e.g. from the alternator, can result in
intermittent voltage drops. One can always in effect directly measure the alt voltage by measuring
the charging light voltage (blue wire at the bulb) when the battery voltage is low. If it's greater
than the battery voltage by more than 1-2 volts, there's a voltage drop from the alt to the battery.

Did you miss this one?

[mysocal911]

Or did you miss this?

Originally Posted by mysocal911

Many seem to forget that there's a large cable that runs first from the alternator to the starter,
and another cable from there to the battery. Either the terminal at the alternator (usually just
crimped & not soldered) and/or loose, or the connections at the starter are loose or need soldering.

Furthermore, you can always crawl under the rear of car and actually try and measure alt voltage
at the starter to the chassis, and then also check the two positive cables (red) at the starter.

[bigel]

Dave, you’ve been very helpful...if you weren’t on the left coast I’d find you and give you a big kiss.

[bigel]

So Dave (socal911) is the winner! So, thanks to Dave!

Turns out the main connection to the starter (from alternator) had worked itself loose and was not making good contact at all. The nut was nearly backed all the way off of the terminal. Turns out the rubber boot that covers the connection was likely the only thing that prevented the nut from backing all the way off.

This condition is what caused the voltage to run intermittently low; sometime right around 13.5 V and other times all the way down to 10.6 V.

Well, I’m certainly glad that I didn’t replace the alternator before discovering the loose connection.

I also wanted to publicly apologize to Dave for reacting to what he likely meant as a good natured jab at my inexperience. I posted a reply that was a bit nasty. So before the community of Pelican, I apologize.

Anyway, I could have just let it lie but I wanted to close the loop on the issue.

[KNS]

Always good to follow up when the issue is resolved - didn’t see this thread earlier...

I had nearly the same issue on my ‘84, it wasn’t holding a charge and it turned out to be the same cable/nut at the starter that was not fuly tightened.