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Installed an engine in a Thing yesterday, having some trouble with the alternator. Owner has a Motorola alternator with three connections at the top, which I'm assuming is the externally regulated model. There's a regulator on the firewall.

My conundrum comes from this - I had left the wires connected and marked. She took them out or moved them to paint the engine compartment while the engine was out. Thus, I have a bunch of wires, and no clue where they belong. I figured out a few of them, but the charging system is screwing with me.

Of course, I didn't have a wiring diagram for a Thing, either, and similar year Ghias and Beetles didn't seem to match up to what I was looking at. Any suggestions.

Actually, luck was not on my side, either, as my multimeter decided to crap out as I was tracing wires, as well.

There are Thing schematics at vintagebus.com, but they're for generator-equipped cars. For your project you should follow the alternator-equipped Beetle diagram (at least for the charging system):
http://www.vintagebus.com/wiring/1303_U ... 1973-1.jpg
The regulator is a solid-state one for an alternator and not the big mechanical "generator" unit, correct?

You'll note on that diagram that the blue wire from the regulator (C1) goes nowhere and the blue wire from the warning light ties into the red D+ wire. This is not a misprint, that's really the way it goes.

This is sort of a weak point with me - anytime I've ever seen a regulated alternator, I've swapped it out immediately for a non-regulated one. I believe the regulator is correct for the alternator, but I can't say that I'm sure.

Now that you mention it, the regulator sure looks like a generator model - are they visually distinguishable from each other?

Are any of the Motorola alternators internally regulated?

If the regulator has B+ and 61 terminals on it it's for a generator.
http://www22.inetba.com/larrysoffroad/f ... Bosreg.gif
You need one with a pigtail that has the D+, D-, and DF wires to go to the alternator. If the alternator has those three connections, it's not internally regulated.
You can use either this style (item #62):
http://www.1800vw.bizhosting.com/0.alt.htm
or the flat-pack one that's about the size of a pack of cigarettes that was mounted under the back seat on `73/`74 Beetles.

FYI: http://www.forparts.com/techbeetle.htm

Bingo, you hit it. I'm looking at a generator regulator. That would explain some of my wiring woes.