Anyone ever use the stock alternator without the relay board?, Racers? Options

[stugray]

I am guessing that someone else has tried this.

I have a stock alternator in my race car for now (upgrading to new 1-wire later). Relay board and entire harness is gone.

I know that I need the external voltage regulator, so I decided I better figure out how to wire it up...
It turns out that the plug from the Alt that goes to the relay board is exactly the same connector & pinout of the Voltage Regulator!

So it can just plug right in... not so fast.

For the alternator to startup/charge, it needs the voltage that is fed from the Alt light in the combo gauge.

SO, can I just wire in a bulb from +12V and splice it into the D+ lead on that connector where it goes into the VR plug?

Then the system should work exactly as before....??
Is the stock Alt bulb a special wattage?

Stu

[stugray]

kg6dxn,

It is not an issue that the idiot light is a diode.
The issue is that the diode lets such a small amount of current flow (it is very efficient) that is does not provide enough current to energize the field winding.

Based on McMarks comment above

Stock bulb is 2W

, that means that the stock setup allows ~170mA of current to flow through the stock bulb and through the field winding when the alt starts up.

But you do not need 2-way current flow.
You need current flow into the field winding to start it.
Once the alternator is generating it's own voltage, it feeds the field winding itself.
This makes zero volts across the idiot light (or my LED) and no current flows any longer (light is off).

I will just put a 70 Ohm resistor across my Diode and that will be enough to kickstart the Alternator.

Stu