HELP fusable link dies while driving

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amoparacer

amoparacer

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Okay so driving the Feather Duster in traffic and fusable link from Pos battery to relay blows. My buddy says alternator may be the cause. Any advise on how to chase is down the short alternator was replaced a month ago so its under warenty. :banghead::banghead::banghead:
 
How big is the alternator? Sticking a GIGANTIC Great Big alternator on top of a 50 year old unimproved Mopar harness just might be a great way to blow things up

Read this MAD article:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

Is it possible the fuse link blew for "some reason" maybe even corrosion, and then was never replaced with one large enough?

Most these old girls go their entire lives without ever blowing one.
 
Replace it with stock rebuild 78 amp wanted the 120 but they needed to order it. My buddy said to remove the power lug from the alternator and test from the lug to a ground with the Ohm meter if its grounding from there its a dead short. So i will try that monday. With the key off and I replace the fuse it blows in 2 seconds. I could not find any bare wires or recent melt evidence any where. I don't think it could be the Mini starter because the key is not on and as I recall the alternator is the only major component thats always hot besides the lug on the starter. The fusible link powers the relay the alternator and inside the car. :wav:

any other thoughts ????
 
A short will not care if the alternator is in circuit or not unless the alternator is at fault; the battery will supply the power to blow the link if there is short other than the alternator. A developing short may have caused the prior alternator to fail.

The good news is that it sounds like you have a hard short so this will be easier to trace. You're on the right kond of track track, to start disconnecting things one at a time starting with the alternator 'til it does not blow. I would advise you to replace the link for now with an inline blade type fuseholder with maybe a 20A fuse and then retry. Changing fuses is a lot better than changing links, and will protect things better as you find this short.

Do you have a wiring digaram downloaded and can you read it OK? That is your best roadmap to troubleshooting this.
 
As soon as the fusible link is connected, power goes to ignition switch, headlight switch, fuse box, lighter wells, and more. Any one of these circuits can cause a fusible link burn open. That's what its for after all.
Just for the sake of mentioning... rain water in the fuse box has caused this too.
First place I would look is lighter wells. Then harness connector for ignition switch located under the column, then headlight switch harness connector.
 
OK, so you are saying the fuse pretty much ALWAYS blows when you hook up the battery?

By the way an 80 amp alternator might just cause this

I WILL REPEAT READ THE MAD ARTICLE I POSTED

Here's what you do. Unhook the battery ground. Hook a test lamp in series between the battery NEG post and the engine block. A short will cause the lamp to light. A bad alternator will indeed cause this problem. Unhook the alternator charge wire and see if the lamp goes out.

If this is an intermittent short, unhook the alternator charge wire and safely tape it off, and unplug the regulator and safe off that wire, and drive the car a bit until you are fairly certain you have proved one way or another this is / was the problem.

Also examine the under--hood harness for damage, around hot engine parts, etc.

There is not too many places that can cause a fuse link to blow--- which is the reason they were used.......they were meant as a "last ditch" protection
 
Okay so i bought a test light and 5 blade fuses first i unplugged the alternator no change then the starter no change then all 5 bulk head connecters then I used the test light and still found draw on the blade fuse replacement for the fusible link. My MSD box that was installed in January was the culprit. I did pre plan by not removing any of the stock ignition I just taped up the lead's running to the coil and the distributor and added the MSD. So now I can sent it in to MSD for repair. As for the alternator its still fine and 65 amp so i will feed the charge direct from the battery with a blade fuse and i will be using a plug in the lighter type voltage monitor to tell the true charge and not damage the stock system. Thanks for the advise Bill.
 
Okay well I removed the MSD from the car and its now running fine on the stock ECU so its off to MSD for repair or replacement. Also for the old wiring sake I in stalled 10 gauge feed from the alternator directly to the battery through its own 80 amp mega fuse. Im now using a voltage monitor gauge through the cigaret lighter.
 
CalleD MAXIFUSE here is a picture of the fuse. Holder is 10 gauge wire and a nice Rubber Clam Shell bought them at Oreileys.
 

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Well, keep an eye on that fuseholder and the 10 ga wiring. The blades are probably not really going to hold up very well with the level of charging current from alt to battery. And BTW, an 80 Amp fuse will not protect a 10 guage wire; 40-50A of charging current to the batt and to the car electric load is going to warm up that wire a good bit. Make sure that there are no sharp kinks in that wire, or the heat will concentrate at that kink.
 
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