72 fusible link, burnt jumper gets HOT, ideas?

[MikeZcar]

72, link from harness to starter burnt up, no link to replce, tried jumper wire for diagnosis, it gets HOT fast! Where to look? Son stranded, me old and tired and had a couple Heinekins so no driving tonight.

[EScanlon]

That it gets HOT says you have a major short circuit someplace.

That fusible link did it's job, it's supposed to fail when too much current flows.

You might begin troubleshooting by determining what was recently added...new stereo, lights, etc. and start by disconnecting same. Then you might get the car running.

FWIW

E

[Nissanman]

Please, Oh please, don't replace a ruptured fuse/fusible link with anything but another of the same rating.

It will almost certainly cause a burnt out wiring loom:rolleyes:

What you can do is connect a 12V globe in where the link was.

It will still protect the wiring from current overload but it will also provide a visual indication of the fault.

Just to expand on above post.

The link feeds a pair of fuses which you can remove to isolate the fault.

These are: -

10A - Horn

20A - Signals [flashers]

These two feeds are NOT via the Ammeter so you won't see the high current draw if they are faulty.

At least, that is what the Haynes wiring diagram says:ermm:

The rest of the fuses are via the Ammeter and are: -

20A - PT

10A - RL

10A - HR

10A - HL

20A - C

Feel free to remove any fuse in your fault finding process.

It can't hurt anything and will ultimately isolate the fault:D

Just be methodical and you will be able to narrow it down.

Have any of these fuses blown?

One sure fire fault which will rupture that fusible link is to connect the 12V battery in reversed polarity:finger:

[DeesZ]

A short is most likely, as stated before. But, when it "gets hot", is the car running, or shut down? I only ask because the last one that burnt up on my '72 was caused by a faulty voltage regulator giving me a super surge (which also exploded every light bulb that was on at the time).

I keep a spare fusible link available. I get replacements from Banzai Motors, http://www.zzxdatsun.com/and my local NAPA claims to have them as well.

[MikeZcar]

Got him to pull all fuses, idea was to replace 1 at a time till problem comes back. All fuses pulled, car not running, wire still getting hot. Got him to pull W/R off the alternator, problem goes away. Dead short in alternator or voltage regulator?

He was driving on interstate when heard a "pop" and lost the fusible link. He had been push started 15 minutes earlier after leaving lights on and killing battery. Too much on alt?

It will either get in-line fuse or fusible link(quick as I can get one) NO wire as replacement.

[MikeZcar]

Finally got to the car with a meter. Dead short from hot lead on alternator to ground. New alt and fuse link, good to go.

[EScanlon]

I think that you're not being told part of the story.

From the fault you found, dead short on the hot lead from the alternator to ground, it sounds as though there was a surge of some sort.

Conjecture:

He got a "jump" from someone and (s)he/they figured the Positive pole of the battery was out visible and not under the fender, hooked up the jump battery positve to the battery negative and the jump negative to the alternator.

Alternator's hot lead and fusible link now are the weak link...smoke ensues, fusible blows, alternator wire melts, jump owner disconnects and you get the call..."I don't know what's wrong Dad! I didn't do anything....."

Just a WAG, but ....???

E