Alright gentlemen, after a week of false starts (ha) I know I am out of my depth.
The car:
1966 289 convertible, auto trans, power top, aftermarket radio, LoJack.

The problem:
Battery does not charge. I replaced the battery first, after it tested bad at advance. The new battery would take a charge fine from a jump start or plug in wall charger, but not from the engine. Also, tested ~12v with the engine off, 7.5v with the engine running. Replaced the regulator. Still, never read higher than 12.5. Tested the alternator by bridging B and F, batt goes right up to 13.5. Replaced the alternator. Now, batt reads <12 v with the engine running. This drops to 9.5v when you turn the lights on. Turn the lights off, it will slowly charge back up to <12 v. With a plug-in charger it goes up to about 12.5.

Any ideas?

 

I'd make sure all the wiring is sound, including grounds. Then recheck the alternator, it wouldn't be the first time one was bad right out of the box. If it's still a no-go, buy an electronic regulator from NAPA. At this point, if the circuit isn't working, surrender and take it somewhere. Good luck.

 

But check all your grounds, especially between engine and chassis, make sure they are clean and tight.

Then do a voltage-drop test on each circuit.

www.aa1car.com/library/voltage_drop_testing.htm

I think that is where I read about it. I'm no expert but trying to become one before I wire my car.

 

UPDATE:
Following Mr. Montalvo's advise, I checked the grounds using this diagram

http://www.hammar.dyndns.org/~djhamm...66/66ignit.jpg

I couldn't find the ground for the starter, and the rest seemed good EXCEPT for the ground of the alternator and battery to the engine block, which was about 1.25 turns shy of finger-tight. I tightened this replaced the alternator, but still no luck: 11.5 engine running, 9.5 with lights, 13.5 when you bridge B and F on the new alternator.
I pulled the alternator again, and took it to Advanced. It tested bad, and they gave me a new one. Same. Sh*t. Now is reading 11.75 engine running, 9.75 lights on, 13.5 bridge B and F.

Next step is to try and electronic regulator. If I still can't get it to charge the battery with accessories on, I'll try the good Texan's advice of the drop volt testing. I'll try to avoid this, because never have done it before, I'm not sure I'd trust my own results.

Stupid question: Why can't I just jury-rig a connection b/w Batt and Field on the back of the alternator and get on with my life?

 

O.K. Let's see if I can get this across in a simple manner. You have 12v at the "B term"...according to your diagram this is constant. When you "jump" this power to the "f" terminal, you are energizing the alternator. You see this as 13.5 volts at the batt. This tells you that your alternator is capable of doing it's job. Since you are seeing less than 12v at other times, this tells you that the regulator is NOT doing it's job. If, when you turn the key on, you have 12v at the "b" term, but, it don't charge, your regulator is bad.

Also check to see if regulator has a good ground.

 

Um, guys, is voltage is way low. These cars have a "12 Volt System" because the battery is 12V. They operate at 14V. A full field test should give you about 14.1-14.9V, maybe more depending on temperature. He's at least 1 volt too low. If the full-field was done properly, the alternator is lame.

 

I disagree...these are old cars. They may be capable of 14v but, that is not where they operate.

 

Yeah, even with a brand new battery, alternator and regulator (you know, working ones) I've never gotten a reading of more than 12 and change.

The ground for the regulator was a *little* loose, but tightening didn't help anything. It'll still charge up to about 12.8 on the plug-in, settle at 11.7 if you start it, and drain 'till it dies if you turn the lights on. I still have to check to grounds for the starter and solenoid, but Stepman has me thinking that this is a regulator issue.

The current regulator is brand new, but it is just a $15 four wire from advanced. Maybe I fried it somehow while i was fiddling with the alternator. Tomorrow morning I'll drive out to the NAPA and get an electronic regulator. I'll post as soon as I get some readings.

*Also* Are there any notorious weaknesses in that wiring harness I should be looking for?

 

harris I do not know much about this but I had the same problem. Make sure the firewall to the block ground is good. Once I fixed that I bought a new regulator and replaced the battery on warranty. Worked like a charm.
Once again I do not know any technical stuff but this sounds very similar to my problem I had.

 

The firewall ground seems okay. The NAPA store was closed, so I can't switch out the regulator today. Just for kicks I moved the ground from the top to the bottom mounting screw. No improvement, so I put it back.
There does seems to be some ugliness in the wiring harness, especially where it comes out from the grill in front of alternator. There are parts of the insulation that look like they have melted and hardened, especially on the black/yellow tracers, and it all seems very flaky. I cannot pull the disconnect by the alternator apart. Any way of testing this length of wire?