Real Time fusible link help

[Lka1988]

I seem to be FSM-retarded...

What is the Black fusible link: AM1, AM2, or Main? It's in the little black plastic box... I'm trying to diagnose a short/battery problem, I've narrowed it down to the black link...

EDIT: I guess I'll explain what's going on.

I went outside this morning to go to the store to get some drinks. When I hit my keyfob to unlock the doors, nothing happened. "No big deal," I thought, cause my key fob battery is going dead, so I reached into the open window (I'm lazy), and hit the unlock button. Nothing happened. So I manually unlocked the door and tried to start the truck. Nothing happened. No lights, no beeper, no stereo, no AC, no dash. I popped the hood and measured my main battery voltage: 0.10 V.

I'm pretty sure that battery is shot, so a new one is on the list.

Ended up jumping the truck from my second battery, let it idle for a few minutes, then measured voltage again: 13.10V. I then measured voltage at the isolator: 13.80V. There is a 0.80V voltage drop between the battery and the isolator, not good. As the idle slowly dropped to normal, the voltage drop between battery and isolator dropped down to .40V. Measured voltage drop between big white fusible link and battery: 0.05V. Other links have no drop.

Now, you're probably wondering why I narrowed it down to the black link. I was measuring current draw between the negative post and cable. There's a .3A draw. I can't remember what the normal draw was supposed to be, but when I disconnected the black fusible link, the draw stopped. I already have every fuse disconnected...

[Lka1988]

UPDATE:

I seem to have a major amp draw, coming from the black fusible link. I can't get a reading cause the fuse in my ammeter blows at 10A. I've blown two fuses in the last 10 minutes.

The ammeter reads 15 amps, then drops to 0.



Anyone?

[Lka1988]

Here's what's going on... Now the battery has dropped to ~5 volts, and is no longer blowing my voltmeter's fuse.

1. fusible link connected
2. fusible link disconnected

Big voltmeter is measuring amps.
Little voltmeter is measuring volts. I know, the battery is dead.

[CJF]

I'm pretty much an electrical idiot, but I think I'd get that bad battery out of there before I even trusted any other diagnostics readings.

That's all I got ...

Curtis

[Lka1988]

Oh, both batteries are out.

See, the main problem I found so far is that the black fusible link, "AM1" as I found out, is shorting to ground somewhere before the 50A AM1, 10A Dome, and 15A Haz/Horn fuses...

It's only pulling 4-6 amps...

[Lka1988]

AH HAH!! FOUND the bugger!!

My auxiliary reverse lights were the culprit all along. I had tied the lights into constant power, through the screw in the under-hood fusebox. That screw gets power THROUGH the AM1 FL, then goes into the big 50A AM1 fuse and the 15A/10A Haz-Horn/Dome fuses, respectively.

For some reason, which I will investigate, the reverse light wire shorted...

[Lka1988]

One more quick question... For those of you who have replaced the positive cable, the one that runs between the alternator and battery, how difficult was it? Price?

My current cable is old and crusty, and has a nice voltage drop anywhere between .3V to .8V.

[Ebag333]

Originally Posted by Lka1988

One more quick question... For those of you who have replaced the positive cable, the one that runs between the alternator and battery, how difficult was it? Price?

My current cable is old and crusty, and has a nice voltage drop anywhere between .3V to .8V.

Look at Photoman's alternator upgrade thread. Lots of good information there (and if you're replacing the wiring, what better time to upgrade? ).

http://forum.ih8mud.com/80-series-te...0-150-amp.html

[dfmorse]

There will be a factory formed cable terminal on the alternator that will not be easily duplicated. As per my diagram:

Battery,Fuse, Winch Project : FuseLink

there is a #8 white wire to the 50 amp fuse and a #6 white wire to the black terminal block and then to the Blue fuse link named MAIN. You will have to build two wires with the proper terminations.

...

[Lka1988]

Thanks for the info, dfmorse.

So I went out to investigate this short, but apparently it's gone. I connected the wire and put my ammeter in place of the fuse: 0.0A. Turned on the circuit: 7.5A. Normal. WTF?


I guess it's time to re-wire...

[sandcruiser]

it would be pretty easy to add a wire from the alt to the battery, or better yet, from the alt to a fuse to the fusible link. That would help the alt charge the battery.

then run a different wire from the alt to the main fuse box. to be safe, it is good to put a fuse (or use the same fuse from above) on that second wire.

In any event, bigger wire is better, but any wire will reduce the load on the corroded main and thus decrease voltage drop.