66 Charging Issue

[John912]

I have a 66 911 with a consistent charging issue. Charging light always stays on after cold start and always goes out within the first minute of driving. Only battery voltage when light on (no charging), 13.5-13.7V after light goes out, which I assume is a good output. Light rarely comes on during a drive and only at extended idle, and then immediately goes off when car is driven. Can't remember it coming on after warm start. Confirmed 2W charging light bulb. Idles at about 1000. Belt is tight. Swapped VR with a new one I have in inventory, same issue. Possible loose connection at alternator? Thanks in advance for any help.

[edmayo]

John, you didn't say, but I assume the battery is always staying charged?

[John912]

Ed

Battery stays charged. When I've checked it, output is 13.5-13.7V after light goes out, which is always when I drive away a few minutes after first starting cold.

[edmayo]

Then I wouldn't worry about it. It seems like some cars need the engine revved just a bit before the charge light goes out while others don't. My 71 does that, but my others don't.

[John912]

As always, thanks for the helpful info, Ed

[Nickelplated5s]

2 cents. My 67 does it at idle when cold. If anything check the ground strap.

[John912]

2 cents. My 67 does it at idle when cold. If anything check the ground strap.

Thanks, I know I replaced the battery and trans ground straps with new, and cleaned terminals when restoring the car 10+ years ago, but will check

[304093]

You might try checking the alternator connection at the starter. Mine gets covered in grease leaking from the inner CV joint boot.
The grease gets flung onto the starter connections, and then my alternator light turns on - albeit, glows dimly.
It took me awhile to figure this out.

It's a terrible mess and a pain to clean all the grease off.
Cleaning the grease off thoroughly and resealing the surface of the joint with clear RTV helps prevent this from happening, but it doesn't completely eliminate it.
The early SWB cars didn't have CV joint gaskets.

I drive my car a lot, so this is just another chore to take care of.
Sometimes my CV joints leak, other times not so much.
I should make this an annual inspection, cleaning, resealing thing and then it wouldn't be such a problem.

[ibmiked]

I had a similar issue that was finally fixed by adding the resistor to the charge lightbulb on the dash. Solved the problem instantly and was a known issue for some alternators. YMMV

[John912]

I had a similar issue that was finally fixed by adding the resistor to the charge lightbulb on the dash. Solved the problem instantly and was a known issue for some alternators. YMMV

Can you tell me more about the resistor, where it's fitted and what it does. I am using 2W bulb.

Thanks!