On Sat, 7 Aug 2010 13:53:08 +0200, "Steve Lusardi"
wrote:

Good explanation Stan, but I have to make a correction. First the field is the rotating part and it is driven by the voltage
regulator, which provides excitation voltage to the field through the slip rings and brushes. The light terminal is grounded by
the internal voltage regulator turning on the lamp when the output voltage is less than 13 volts. The Sense terminal is an input
to the voltage regulator. It is the control of the system and draws current from the battery. Therefore, it must be switched or
the battery will discharge when the engine is turned off.
Steve

Not completely correct , at least on the nippondenso. The Lamp
terminal is a voltage output. Until output reaches roughly 13 volts it
is grounded - but then it OUTPUTS a voltage, which cancels the voltage
fed to the other side of the bulb - battery voltage on one side of the
bulb, and charging voltage on the other side. If the wrong bulb is
installed you will sometimes see a transitional "dimming" of the bulb
at low speeds/outputs.

wrote in message ...
On Fri, 6 Aug 2010 14:44:13 -0700 (PDT), wrote:

On Aug 6, 2:55 pm, Sunworshipper wrote:
I'm about to dive back into my main convenience once again, last time
it took about 40 hours of work. Before the problem was that a diffuser
plate that protects the electrical from melting on the back of the
alternator had rusted off the exhaust manifold and then dropped down
and got caught by the main power to the alternator and the frame, thus
shorting out intermittently.

Does anyone know exactly what an alternator wants and when? The main
fusible link had melded down and I might have weakened / let out some
magic smoke while hooking up the main power after having the
alternator tested. Seems the main power is off till the engine is
running and I put it power all the time for a second or two. But, it
worked and was charging for a awhile and now the charge light is on
again. Tested with a meter when it was fixed and now, so the dummy
light is correct.

I got a stick and pushed the three lead plug in, thinking it might not
have snapped in, and it smoked a bit. Weird, but this thing is
operating in extreme conditions as in oil spray and sand. Maybe I
should just replace it once a year till the vehicle dies.

There was another intermittent thing I noticed when the whole vehicle
had its guts hanging out, that one of the two powers that go through
the ignition switch can be altered when moving the key back and forth.
Tried wiggling that to see if the light would go out.

I found one site that almost gave me what I needed. Where the three
wires go and the main power, but not when where and why. I'm pretty
sure the regulator is in the alternator, btw.

At the moment all I can think of is look over the wiring again and
have the alternator tested again, or maybe buy another, but afraid to
toast an new one cause I missed a short or something on this
nightmare.

SW

Without a circuit diagram, you're ****ing in the wind facing the wrong
direction. You have no idea what runs where. Classic-style
alternators need voltage on the field windings to make juice, so have
a battery connection. Current permanent magnet ones are more like
generators in that they can generate voltage anytime. Voltage
regulators can be on/off style using relays, on/off using transistors
or regulate winding voltage to control output voltage. Regulators can
be external or internal. Latest alternators have everything inside
and one wire out. Parts may or may not be replaceable. Give us a
hint as to the make, year and model and there might be some more info
forthcoming. Some info may not be available outside a dealership,
too. Too much has gone into the "plug it into the computer and see
what it says" method.


He said it's a Toyota, so it's definitely not a permanent magnet
"alternator" and it will either have an internal regulator (99%+
chance) or a regulator in the PCM.(Computer).
Best bet is it is an integrated regulator in a Nippondenso alternator.
The fat wire goes directly to the battery, through a fusible link, and
should have power at all times. The 3 wire plug has one wire to the
charge light, one to switched ignition, and the third is a "sense"
wire.
They should be labelled L, IG, and S, respectively. Looking at the
alternator connector, with the connections like a "C", the top is the
L, the bottom is the IG, and the "back" is the S on MOST Denso
alternators. The L can be connected to the IG if no charge light is
used, and the charge light, if used, should turn on when it is
grounded. The L terminal should have 12 volts on it whwn it is
charging.

A u-pull-it yard is a God-send for this kind of thing, you can see how
things were hooked up originally. If you're moderately lucky, nobody
has hacked the wiring before you, either. Grab everything when
parting out, wiring as far as can be grabbed and all plugs and
connectors, all bolts, nuts and brackets, too.

Stan