Finding electrical short

[Yukon Jack]

Driving my 69 home last night in a light drizzle it started to idle a little lower than usual. Idle was a little rough but not bad. As I came up to a light, I lost all electricity. Got out, opened the hood and see a little smoke coming from the fusible link off the + battery post going to the little black electrical block on the side of the fender.

A guy immediately stopped and pulled me over to a little used tire store in the not so good part of town. They had some fusible link but it started to burn as soon as it was attached.

My buddy with the 71 1 ton Chevy 4x4 came to drag my truck to my house, driving his . . . well, I'm so ashamed to say, his 1 ton Ford. I naturally fainted! When I came to I had sense enough to not want to leave my truck at this tire store over night for fear of it being stripped in the morning (oh, there was a adult book store right across the road speaking of stripped), so I let him drag me home with the Ford.

So, how do I go about finding the short? I'm electrically stupid, imagine that.

Is it best just to get it to an auto repair station and let them do it?

[71GMC_3/4T]

Get yourself one of those 12V test lights with the alligator clip and screwdriver handle with a point.
Disconnect the fusible link.
Put the test light between the batt + and where the fusible link was attached.
If you have a short, the light will light up.
Start disconnecting potential shorted items until the light won't come on.
Disconnect the "battery" wire to your stereo to keep that from confusing you.
Take out the dome light also.
I'd start with the big red wire on the alternator and/or disconnect the plug to the regulator if you have an external one.
You could start unplugging fuses, but they should have blown before smoking the fusible link.
The heater motor draws a ton of current when it's on hi. Was it on?
Follow that big red wire across the front of the engine compartment and see where it might have abraded the insulation.
You can fix it I'll bet. You just needed to know how to look for it...
While you have the fusible link disconnected and the light in, nothing will work inside the truck since it has to draw the current through the resistance of the bulb, which will limit the current to less than an amp.
Good Luck!

[Yukon Jack]

Heater was on hi with difroster switch on. Haven't used the heater fan until today . . . hmmm. Also was using the wipers and headlights.

[71GMC_3/4T]

I think you're on to something. My guess is you compromised the fusible link by running all the accessories and then when you tried to go back to normal it had more resistance and got hot.
I had a 74 chev monte carlo that had the headlights get really dim one morning on the way to work. When I turned off the heater (was on hi), the lights came back up. The heater can draw upwards of 20 to 30 amps on hi. My problem was due to the alternator belt slipping, but it's a similar problem.
Also, your old wiper motor is probably pulling more current than when it was new since the lube has turned into thick greasy mud.

[Yukon Jack]

With everything off as soon as the fusible link was attached it started to go. So should I do as you said above and then start checking the headlight wires, heater fan and wiper motor?

Last fall I put on a remote starter selonoid along with new positive battery cables from the battery to the selonoid and selonoid to starter. All that wiring looked fine with a quick inspection. That ought to help in narrowing down the prolem, I hope.

[71GMC_3/4T]

If the FL starts to go as soon as you hook it up with everything off, it probably isn't the wiper or fan since they should be off via their associated switches as well as the ign key.
I'd start with the V reg. It may have fried when you were loading the system with all the other stuff running. Could also be headlights since they are on a rather large breaker usually.

[Fred T]

To check circuits for shorts first disconnect the battery. Then, with the item switched off, use an ohm meter to check from positive to ground. Example: taillights. Remove both bulbs, check both wires on each side. This works best with a buzzer box that buzzes when the circuit is closed. Hook one wire at the switch or fuseblock, the other lead at the taillight. Then you can crawl underneath and start wiggling the wires looking for intermittent shorts.

[Yukon Jack]

I did an updated post on this subject yesterday or on Saturday. I had a second to look on Saturday and immediately noticed the batter cable going from the remote selenoid to the selenoid was laying against the frame. Moved it and saw it was rubbed to the wire. The motor is coming out in just a few days so I put a plastic flexible conduit over the wire, then replaced the fusible link.

Flipped the headlights and they came on. Fired it up and then very soon after a lot of smoke started coming from under the hood. Got out of the truck and the fusible link is completely glowing along with the hole wire it is attached to. Then the alternator started to smoke real bad. As I wondered why I didn't have a fire extinguisher, it finally stopped burning wires. Looks like it melted the whole wire from the battery to the alternator. The bolt where the wire goes into the back of the alternator is loose now, so I'm wondering if it toasted the inners of the alternator.

The alternator is going with the engine so that's not a big deal but I don't want this to happen to the new engine and alternator. Bummer.