FastKat

iTrader: (10)

I wired up my Camaro alternator tonight (from a 1999 Camaro) and it looks like it works! The battery reads 12.7 volts before starting the car (just took it off the charger) and after starting it, the voltage measured at the battery jumps to 14.4 volts.

However, the battery light on my dash does not come on before I start the engine. I wired it up just like on the Camaro wiring diagram, which runs a single thin wire (not the heavy charge wire) from the alternator to the dash light. The other side of the dash light is to +12 volts. I have tested the light by taking the thin wire off the alternator and grounding it to the chassis, which does make the dash light come on.

This all suggests that it's wired correctly, and the alternator isn't turning on the battery light before I start the engine. Why is this??

I also installed a 470 ohm resistor in the thin alternator wire, which has been discussed many times on this forum... initially coming down from the guys at Speartech.

Why isn't my battery light coming on before I start the car, with the key in the "run" position?

downset71

you prolly dont need the resister if you are using the dash dummy lite! same thing....

FastKat

iTrader: (10)

I was thinking the same thing. I measured the resistance of the light, and it was only 30 ohms. There might be a resistor in there with the light. Speartech recommends 470 ohms. Regardless, I don't think 30 ohms is enough?

470 ohms + 30 ohms = 500 ohms... is that too much?

downset71

oh, didnt realize factory bulb OHM rating was so low... i would say change the factory bulb just to make sure. BTW, what car is it in? also try testing the thin wire while car is running to see if it is putting out any voltage or ground..

FastKat

iTrader: (10)

I am not 100% sure what the Camaro bulb resistor is, but I bet it's around 470 ohms if that's what Speartech recommended.

The car is a 1985 Jaguar XJ6. The factory bulb I measured was the one in the Jaguar, and it came out at 30 ohms.

That's a pretty good idea. I did test the continuity of the wire, but that doesn't rule out a bad connection at the alternator. Actually, the alternator might always have that wire grounded, even when the car is off. After all, the battery light gets its +12v when the ignition is turned on, not from the alternator. That actually leads back to my initial question...

What makes the alternator ground that thin wire, which turns on the battery light?? Does it have to go below a certain voltage, or does the alternator have to be not charging properly?

G-Body

iTrader: (4)

Ditch the resistor and the light should light up just fine. You either need a light or a resistor. The GM light is a standard 194 bulb, I don`t remember how many ohm`s of resistance it has, but it is no where near 470 even though the resistor that gm would use in place of it is 470.

downset71

just for an experiment, ditch the factory dummy lite. take the wire from the alt., run it thru a temporary pigtail with a marker lite plugged in, and run other end to a + connection. see if that works, so we can rule out your vehicle's dash setup.

FastKat

iTrader: (10)

Thanks for the info guys. I tested the dash light and it works fine when the wire (before the resistor) is grounded.

I didn't really want to cut the wire up and change out the resistor, but I guess I'll give it a shot. I have enough slack to probably do it one time. I won't be able to get around to the car for a while, but I'll let you know how it turns out.

FastKat

iTrader: (10)

So I finally cut out the resistor and ran the wire straight to the battery dash light, and the dash light still does not work. I then took out my plug and tested for a ground directly off the pin on the alternator, and still no ground. I went to the parts store and tested a brand new alternator, and still no ground. WTF?!?!

Any ideas?! With the 470 ohm resistor wired to the dash light, my system was at 14.4v at idle.

Do I even need the resistor on the 99-02 F-body alternator, or is that resistor only for the 98 alternator? I didn't realize until I checked, but the 98 dash light is controlled by a "solid state" device, while the alternator wire runs directly to the dash light in the 99. Maybe that solid state device has no resistance, and is the reason only the 98 alternator needs the resistance in the line, which is provided directly by the bulb in the 99-02 cars.

FastKat

iTrader: (10)

I figured out what I was doing wrong. There are two different pins that can be used on the LS1 Camaro alternator. One does not operate the dash light, and one does operate the dash light. I was trying to use the wrong pin to turn on my dash light. See my post here for more info:

https://ls1tech.com/forums/14588749-post87.html