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----- Original Message -----
From: "Ed Anderson" <eanderson@carolina.rr.com>
> I've been working with Tommy James on his alternator problem and the
> question came up (it always comes up) - do we need the diode and relay
shown
> on the Mazda alternator wiring diagrams. It appears that if you are using
> the Mazda alternator (mine is Bosch rebuild) then you do indeed need the
> diode (and the relay if you want an lamp indicator) in the circuit going
to
> the "L" (Lamp?) terminal of the alternator. You certainly need the "L"
> circuit to provide voltage to the alternator for the following reason.
>
> With the engine off, a current from the battery flows in the "L" circuit
> closing the relay and thereby turning on the lamp (to indicate no charging
> when the alternator is not running), and then throught the diode to the
> alternators field coil (internally). This current provides the "initial"
> starting current for the field coil of the alternator. Once the
alternator
> starts producing its own voltage then the regulator switches to using the
> alternator's internally generated voltage for regulation. The "L" wire
then
> has essentially equal voltage on both sides of the diode which turns it
> "off" stopping the current flow through it and the relay causing the
"lamp"
> to go out.
>
> For this reason, it is probably not wise to put a lamp directly in the "L"
> circuit of the alternator (if it is one of the type described) because
> should the lamp burn out or otherwise cause an open circuit, the
alternator
> field coil will apparently not get the initial starting current and will
> fail to generate voltage.
> Thanks to Tommy James for causing me to research this a bit more as I had
> always wondered whether the "L" cirucit was needed if you didn't use the
> "lamp" feature. It turns out it is on this alternator!
> .
> .
> Ed Anderson
> Matthews, NC
> RV-6A N494BW
> eanderson@carolina.rr.com
I never investigated this either Ed. I mearly duplicated the circuit as
used in the car in order to get it working.
Tracy
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