Looking at the schematisc on page 91/ 92 of the Chilton manual, I too am using an LED instead of the lamp and  lamp relay. I don't use the diode, just a LED and a 470 ohm resistor in series. The diode is only needed if you use the relay (or a lamp). Then a 1N4004 should be more than plenty.

The idea is that a current will flow from "+" of the battery through switch, through resistor, through LED and through the field coil to ground until the alternator starts to produce voltage (through the diode trio), which brings the voltage on that side up to or above the battery voltage so the voltage across the LED is zero or reversed.

If the internal regulator (power transistor) is bad or is not getting battery voltage at the "R" terminal the LED should not light at all (unless you've connected it wrong - reversed Anode and Kathode).

Connections to the alternator: the top of the "T"  is "R" and is supposed to go to battery via ignition or master switch. The vertical bar of the "T" is "L" and that's where you connect the Kathode of the LED and then via a resistor, the anode to the battery via ignition or master switch.
Remember, an LED lights up when the current flows in the opposite direction of a normal diode (and acts as a diode when then current flows in the direction of the arrow, plus to minus.)

Man, I wish I had written this better.

Finn

John Slade wrote:

I'm still having trouble with my alternator warning light.

I know we discussed this before, but would someone refresh my mind?

Currently I have an LED in the circuit as the warning light. It doesn't go out. Buss voltage seems fairly stable at 14.2v with engine running. Do I need a regular bulb rather an LED, and what are the specs of the diode shown in the schematic?

John Slade (hit 25 mph last night)