What else can you do with a late ’70’s Z-28 hood scoop?

How many wires do you need connected to an alternator?? 😮

Allen I was being a bit sarcastic, I don’t know if you saw the photo in the link where it looks like there are about 10 leading to or from the alternator. Almost like they are using more than one wire together to make up for too-small gauge.

Alternator? What’s that?

Sounds like your alternator does not have a built-in regulator, Allen. Mine does, and you’re supposed to remove the external regulator from the circuit, leaving only the hot charging spade connector, and the screwed on ring terminal ground. You simply connect the hot wires that were on the regulator previously.

When I replace my dash and clean up the wiring, I plan to run a new hot wire all the way to the battery up front, because I’ll also be removing the ammeter and replacing it with a voltmeter…

Kent, Where does your alternator warning light connect to?

Ok, Allen, I went looking for any installation instructions that might have come with my alternator, and couldn’t find any. So, here is how I THINK it works ánd should be wired. Note that my new engine has not been installed, only run on a test stand, so I haven’t wired it in, much less tested the alternator.

Though mine is called a single wire, internally regulated alternator, it actually has two male spade connectors side-by-side that likely are intended to be connected with a single round plug-in connector that actually has two connections within it. The larger spade connector is for the actual charging circuit, where you connect the heavy guage red wire. The smaller spade connector beside it is where the green idiot light wire connects. Further, there’s a screw on the body of the alternator where you connect a ground wire with a ring connector.

If replacing a generator, you remove the external voltage regulator, and join or splice the heavy gauge red wire from the alternator to the heavy gauge red wire that runs from the other side of the regulator to the front of the car and the battery. You splice the smaller guage green wire from the alterator to the smaller guage blue wire on the other side of the regulator that comes from the ignition switch through the idiot light.

When you turn the ignition switch on, it provides power to the idiot light, and provides the necessary excitation for the alternator. The circuit is hot, seeking ground. Without the engine running, producing power, the idiot light grounds through the alternator, and the light comes on. Once the alternator starts producing power after starting the engine, the spade connector the idiot light wire connects is now hot, not a ground, and the light goes out. If charging is intermittent, the grounding provided is intermittent and the light flickers on and off… Note that there’s an internal diode in the alternator that protects the alternator as this idiot light circuit changes from hot to ground and back…

This is similar to how the idiot light for oil pressure works. The wire is always hot when the ignition is on, and it grounds to the engine block through the sending unit when the engine isn’t running. After the engine starts the oil pressure pushes a spring-loaded plunger in the sending unit out, interrupting this ground and the warning light goes out. If engine oil pressure is too low to keep that spring loaded plunger pushed out, you’ll get a weak or flickering light, as it can’t get a good, consistent ground.

If you look at the back of a factory speedo for a VW you’ll see a curved, isolated copper bus bar that the little idiot light sockets/bulb holders push into. This bus bar has a male spade terminal on it, where the hot wire from the ignition switch plugs in. When you push in the light bulb holder/sockets into the back of the speedo, they contact this bus bar, providing power to the outside housing of these light sockets any time the ignition is on. Each plugin socket has another male spade connector on the back that is isolated/insulated from the metal housing. This is the lead for the single filament in each bulb. The wires coming from the engine for the oil pressure and alternator/generator idiot lights connect to these spade connectors, providing a ground through the filament of the bulb back to the engine at the rear. This is the exact opposite of what you’d expect, and how the other lights work, whether dash illumination, high-beam indicator, turn signals, etc. For those, the metal socket/bulb holder provides the ground, and current to illuminate the light comes through the spade connector on the socket to the filament in the bulb. Such is the weirdness of a circuit seeking ground…

You asked me what time it is, and I gave a lecture on sundials. But, I hope it helps with understanding which direction the electrons are flowing, and why..KentT2015-03-13 21:14:52

Just ran across this pic of the back of a VW speedo. It shows the curved bus bar that provides power to the outside of the idiot light bulb holders that are seeking ground.