Alt light question (wiring/splicing a brighter LED bulb)

[Plavan]

Just a quick question on the Alt light. Does anyone know which wire is the "hot" wire on the Alt blub (1969)? I'm keeping the original there, just splicing in another warning light. I just wanted to check before I dig into it. No need to reinvent the wheel . I am splicing a red LED (5 actually) strip to put on the dash to get my attention better if I were to throw a belt while racing... It has happened to people I know and their heads get toasted.
Thanks in advance.
Chad

[Brant]

we put a 2nd warning light on our race car for just this exact reason.
we used a shift light (bright.. lots of volts though) with a blue cover on it.

the thing is that the alternator warning light is really designed to carry a very specific amount of current.

its more than just a warning, it is also the feedback loop that excites the alternator.

if you change the total voltage (by changing bulb size or adding bulbs) bad things will happen to your charging system

when we did ours we had to run a very specific resistor in line to replace the bulb and then used a relay to turn off an on the warning light.

LED's may or may not be safe since they draw so little power, but this is a delicate and sensitive set up.

be cautious.
brant

[Early_S_Man]

Blue D+/#61 wire will be the negative wire, and Blue/Yellow will be the '+12 Volt bus wire' ...

How big a dropping resistor are you using? There should only be 20 mA going through the LED string, right?

[Plavan]

So I should just splice the blue/yellow wire and hook it up to the LED, then ground the LED? I'm keeping the orginal alt light there.
I know the Alt light works differently since when it is "on" it is not getting any Alt power...etc.
I know about the quirks of the chraging system, thats why I figure LED lights would be the best bet because of the virtual low power drain.
I'll just use my good ole' trusty test light and figure it out.

[Early_S_Man]

Chad,

If you ground the LED string ... they will be on all of the time!

A 200 Ohm 1/2 Watt dropping resistor and negative side wired to the Blue wire should work fine.

[Plavan]

Thats what I meant

[304065]

Chad, if you want a belt breakage detector there are better ways to do it. The voltage regulator can get hot and drop out, which will cause you to pit because you think the belt is broken.

Why not the belt breakage system from the 964?

[Plavan]

I am not familiar with it. Could it be adapted to my car for a reasonable price?