TR battery not charging diagnosis

Hey folks, 10 minutes to driving the new-to-me ‘88 TR to get it registered the charging light came on. My cigarette lighter VM shows voltage dropping from 12V down to 10 in a few mins.

Made it back home, charged up the battery and trying to diagnose if it’s an alternator/rectifier issue or something else. The alt belt is still on and spinning, and VM at battery confirms ciggy lighter readings. Given the position of the alt, (and presumably the rectifier is inside it?), is there a good diagnosis point where I can isolate and check alt voltage? What other steps can I take to confirm it’s the alternator and not a short elsewhere or other issue?

BTW, I saw a thread where Steve suggested checking AC volts, both my digital and analog meters show 24-25 VAC.

Prior to this the car ran fine but I did notice that all external lights would flicker while the car was cold idling, not sure if that portends anything or if it’s just the nature of the TR’s charging system.
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Looking at the workshop manual, it appears that the alternator output wire joins the battery circuit at the starter terminal.

No 50 on the schematic says:
“50 - Alternator charging circuit failure optical indicator (L. 12V - 2W red)”
Is this the dashboard battery warning light or something else?
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So I pulled the alternator and took it to an Autozone to test, they’ve confirmed that it’s not working. The youngster was unable to be more specific. There appears to be a replacement available for about $100. IF you’re in the US, would the tribal wisdom be to take to an old school alternator/starter shop for a rebuild or buy new?

Interestingly, I did not have to remove engine mounts and lift/drop one side of the engine like the other threads mentioned, I found enough clearance to extract the pivot bolt.



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Having trouble reinstalling the puppy, posted here

https://www.ferrarichat.com/forum/posts/150133019/

 

Went with the rebuild option at a local shop. He said all diodes were gone like as If the battery cables were reversed.

That’s got me concerned. I do remember connecting a modern battery tender reversed, but that immediately blinks and shuts off if it senses reverse polarity. Besides, I was driving the car fine after that when the battery light suddenly came on. While removing the alt, I did forget to disconnect the battery and shorted the cable to chassis, but by then the alt was gone anyway.

What tests can I do to ensure the new alternator won’t blow up?

With the battery disconnected I’ve checked with DVM:
- Alt to starter shows continuity
- Alt to ground shows open circuit (I assume the initial fluctuation is due to capacitors, it settles into open circuit)
- Battery still disconnected, positive to negative terminals show open circuit with DVM, but with an old analog Ohm meter it appears to show some reading ??
- the Anderson plug connecting battery to alt/starter has been replaced (new outer plastic clip-together insulator plugs, inserted existing terminal lugs into them),

Any known trouble spots for shorts besides the infamous fuse box?

And is there a typical discharge or leakage amps I can expect to see when I get brave enough to connect the battery?

 

lol, after the struggle getting it back in, I just wanted to avoid doing it again. Anyway, got everything buttoned up and went out for a drive, pleased to say everything is fine again.

I’ve see the kirkit values somewhere in the manual, but I’ve never had success using that damn thing on my other cars (access plus repeatable readings), I’ve set to the snug side for now.

Greatly appreciate your help Steve, I’ve read up on many of your other posts, your wealth of knowledge AND the effort it takes to reply is commendable. One of these days I’m going to have to drive down from Dallas to Austin and buy you drinks and dinner.