Questions about fusible links and other electrical issues

[gavio]

Does anyone have any information source to reveal the correct gauges/ratings for replacing fusible links? My wiring diagrams and service manual are both mute regarding any relevant details and the wires are unlabeled. I can eyeball and guess, of course, but I'd prefer some facts if I can score any.

This post is related to my earlier post about my catastrophic electrical failure. With some clues from y'all - thanks, as always - I'm down to the fusible links.

Of the two that connect to the alternator's 12v wires, one is completely burned away and the other is toasted looking so they need replacement before I'm gonna get much further.

Also, out of more idle curiosity, what are the reasons for choosing either fusible links, fuses, or circuit breakers for all these various circuits? I have theories about why one and not another, but facts would be better.....

Thanks again.

[gmctd]

Look on the large plastic insulator where the fusible link joins the wire.
The number there is the link diameter in metric or awg size.

Fusible links open at the source, protecting the harness wiring. Damage there usually requires more than casual owner response.

Fuse opens at the load, protecting the device, or at the panel, also protecting the power source wiring into the panel.
Usually owner serviceable.

[gavio]

Thanks for the answers, man. I'm a little confused though by what I see when I read those numbers as i have two of them that are visibly different sizes yet both say "16" on them and both appear to be larger than 16 gauge wire - one is on a wire that seems at least 12 ga. and the other seems more like 8, maybe10 at the smallest.

Any thoughts?

Also, how do you replace these? I have a good theory on what caused it to come unglued but I need to put it back together to find out. My auto parts house has fusible link wire but in my earlier thread, someone said he had trouble with just soldering in new inserts.

What to do?

Thanks for any help.

[gmctd]

Each large wire will have a 16ga fusible link - you can use crimp connector, then RTV it.
Cut the plastic off, strip back till you see fresh copper wire.
Don't crimp to burned\blackened copper for best results.

Make sure it is '16', and not '1.6', which would be in mm. 1983 may have either standard.

[NH2112]

The gauge rating refers to the wire itself and not the insulation, which is most likely what's making the wires you have look thicker than they should.

[gavio]

Thanks for the information again. I went over and got my new 16 ga. fusible link wire and you're right, Phil, the thickness of the insulation was confusing me a bit. What also was confusing was the notion that there would be the same gauge fusible link attached to circuits of two different gauges (in this case it turns out they are 12 ga. and 10 ga.) as well as the idea that the main charging circuit would be flowing through such a small link.

As I sit with it, though, I see that the way it's stuck together, under charging conditions only some current actually flows through the link to the batteries while most of the alternator's juice actually flows via other paths to the remainder of the vehicle.

I'm thinking that what caused the problem is that the electric feed for my veggie-oil system, which includes a heater (which can draw as much as 30 amps in brief spurts), was connected to the same junction block. What may have happened is that the heater may have been drawing along with everything else a bunch of extra current through that poor link. My hunch is that it didn't show up with the old alternator because it didn't put out all that much juice, but with the new souped up model which has a lot more capacity, the circuit went hog-wild.

My plan is to splice the power for the veggie system into the alternator charging wire at the same point where the remainder of the vehicle power branches off - this way the heater only draws directly off the alternator, leaving that last part of the circuit the way it was in the first place.

Then again, I could be on the wrong track entirely - we'll see.......

[Larry Andrews]

Gavio, Where did you get your schematic from? Sounds like yours is useful. I've got the chilton manual for the vans but it's pretty weak as it's got most of the circuits split apart from each other with little way to figure out how they're connected.

tks, la

also an 83 G20 with 6.2, btw

[gavio]

Well, Larry, "useful" is a bit of an overstatement, but these are certainly better than Chilton's. I don't know where they came from - they were with my van when I bought it. They are xerox copies of some kind of CAD-type drawings on ledger-size paper. The plus side is that pretty much everything is represented on them somewhere. The down side is that it the objects and lines are not really arranged like they are on the car so it takes quite a bit of studying to identify what corresponds to what.

I'd be happy to copy these for you if you wanna throw in a couple bucks for copies and postage. The schematics for G-vans occupy several sheets.

[arveetek]

Gav,

Make sure that you have a good body to battery ground. On the pickups, there's a small wire that goes directly from one of the negative posts of the battery cable to the body. I had wild voltage fluctuations as well, and it finally turned out to be a bad ground. My headlights would dim and brighten, and the voltmeter would read from 12 to 14 volts.

I would suggest taking your veggie loads directly off the battery, and not off the alternator. The batteries are the true source of clean power, and the alternator isn't. The alternator doesn't put out clean voltage by itself, but the batteries help filter it. Plus, I think it would be harder on the alternator.

Casey

[gavio]

Thanks, Casey, i just went out and looked - the battery to body ground seems to be in good order - solid with no significant corrosion.

I'm nervous as h... about driving this thing any distance without having a decent idea what's going on, i must say.

I will change the veggie power hookup, however, your thought makes sense.

Thanks for the help.

[Eric Deslauriers]

Originally posted by arveetek:
Gav,

I would suggest taking your veggie loads directly off the battery, and not off the alternator.
Casey Casey makes an excellent point. All elevated loads should come off the battery side and be fused (of course).
Not sure where he saw this tho. smile.gif