A resistor is your friend, Hey Daze

Tubo

Bullet Bob wrote:

I do use an LED for the Alt. Light and, yes, I had the same issue.  Since I already had bored a hole for the LED I didn't want to change so I came up with a much more complex solution...whoda thunk?  I used a Bosch relay coil as the normal incandescent lamp filiment and let the relay switch the LED on when not charging.  Soon as the alternator spools up the relay drops out and the LED goes off.  Got a diagram if anyone wants.
I think the problem witih the LED is that they will fire with a relatively low potential difference.

I installed an LED charge lamp per BB's diagram (LED operates via relay), works as intended.  Note that I have a GM 10SI alternator. 
I had had an incandescent light bulb w/o the relay and it worked fine until the voltage regulator started to allow the alternator to put out 18v and burned out the bulb.
 

Nos681 wrote:

Can someone explain the 5 gauge cluster portion of picture?

I don’t get that portion.

The regulator uses power through a resister as part of its control.  with an idiot light the actual bulb is the resister.  With an amp or volt gauge there is no bulb and thus no resister so one needs to be added.  Make sense?
 

Daze wrote:

Bullet Bob wrote:

Got a diagram if anyone wants.

I would like to see the schematic.
 

My car has neither the volt meter or the two terminal ammeter.  It has the inductive ammeter.

Daze wrote:

Nos681 wrote:

My car has neither the volt meter or the two terminal ammeter. It has the inductive ammeter.

I have that too. You still need some sort of resister on the I terminal.

The wire on the ignition switch that goes to the "I" terminal on the alternator also is the ignition switch feed to the ignition coil.  With the engine running, and the alternator providing power, the "I" terminal will have enough voltage that will extinguish the alternator light, if installed. The resistance of the light is enough to prevent a back-feed to the ignition wire at the ignition switch that would keep power on the ignition coil and will enable the engine to continue to run with the ignition key "off".  If you do not have an alternator light, you need a resistor to prevent this voltage from feeding the ignition wire.  As indicated in the diagram, a resistor in parallel with the light will enable the alternator to function if the light burns out. 
Send a PM to me with your email and I can forward BB's LED alternator light circuit.  I did this conversion on my Mustang and it works just fine.

wsinsle wrote:

BobE wrote:

Daze wrote:

I have that too. You still need some sort of resister on the I terminal.

The wire on the ignition switch that goes to the "I" terminal on the alternator also is the ignition switch feed to the ignition coil.  With the engine running, and the alternator providing power, the "I" terminal will have enough voltage that will extinguish the alternator light, if installed. The resistance of the light is enough to prevent a back-feed to the ignition wire at the ignition switch that would keep power on the ignition coil and will enable the engine to continue to run with the ignition key "off".  If you do not have an alternator light, you need a resistor to prevent this voltage from feeding the ignition wire.  As indicated in the diagram, a resistor in parallel with the light will enable the alternator to function if the light burns out. 
Send a PM to me with your email and I can forward BB's LED alternator light circuit.  I did this conversion on my Mustang and it works just fine.

I don't know how the internal of the 3G works but this is what I kinda of thought. You put +12 volts on one side of the light bulb form the ignition switch, the other side is tied to ground inside the 3G and the light bulb lights. Now when the 3G fires up the internal ground goes away and maybe goes to +12 volt and the light goes out. Now if there isn't a light bulb or resister; the ignition wire is +12 volt, the 3G is ground, you will blow a fuse or burn up a wire. This is just a guess because I don't know the internal of the 3G but what BobE says makes sense too.

The ignition switch wire provides the +12v to the light bulb (and parallel resistor) and to the alternator field (rotor) and to the stator through a diode bridge (the other side of the diode bridge is grounded).  The diode bridge is necessary to convert AC produced by the alternator to DC used in the car. 
Once the alternator is spinning and providing power, the stator provides power to charge the battery and drive the accessories.  The stator and field are connected to the electronic regulator that also will back feed the ignition switch wire (bulb and resistor).  The presence of + voltage on both sides turns off the bulb. 
If one has an MSD box, a diode is installed in line with the bulb to insure the MSD box does not continue to provide ignition power.  If one is not using a light, a diode should be installed to prevent the back fed voltage to the ignition switch.