fusible link

chad · Jun 11, 2015

OK let me start off by saying I am horrible with wiring. I was at a cruise night the other night. Car has been running great. But when I went to jump in the car to leave it rolled over and over like no spark. I thought the coil wire was loose. I shoved it on further and it fired right up. So I drive it around stop to see a buddy and went to leave again. Same thing rolled over and over and then it lit up. Drove about 500 yards and 2 big bangs out the exhaust and lost all power inside the car and smelled smoke . No lights no nothing. Drag it home and look in the morning the fusible link wire on the firewall was fried. I can't find any shorts bare wires or anything. What else could it be ? I am stumped.

Shorthorse · Jun 11, 2015

Year, Make & model?

747mopar · Jun 11, 2015

A loose connection will create heat and melt the wire, if it's at the bulkhead then there's a good chance the connector has seen it's better days (common place for issues). If you confirm that it was at the connector then you can drill the hole straight threw the bulkhead and run the wire straight threw. If it was anywhere else keep looking, do you have many added electronics or a bigger amp alternator that could of exceeded the wires capabilities?

chad · Jun 11, 2015

Its a 65 coronet 500. There's nothing added other than an electric fan. I checked for loose terminals and couldn't find a one . It has the battery located in the trunk. But in followed the cable all the way through no issues there either.

747mopar · Jun 11, 2015

Where did you connect the fan power? It needs a source straight from the battery (they pull allot of amps). If it was close to the bulkhead I'd still take it apart and check the terminals, like I said they are prone to getting loose and dirty over the years.

chad · Jun 11, 2015

The electric fan is straight from the battery with a fuse and switch. I didn't hook it up that's the way I got the car. It melted the Link wire close to the bulk head. Instead of putting a fusable link back in it. Is it possible to put and in line fuse set up on it ?

747mopar · Jun 11, 2015

Yeap, I won't use fusible links and used an inline Maxi Fuse instead but check that bulkhead out.

chad · Jun 11, 2015

How many amps should the fuse be just so I don't over do it and cook something else lol. I will recheck that at the bulk head again tomorrow.

Dennis H · Jun 11, 2015

Take that bulkhead off carefully, don't break the ears. Spray the crap out if them until it runs clean with electrical cleaner.

chad · Jun 12, 2015

I would imagine a 30 amp fuse would suffice in that fusable link wire ?

hunt2elk · Jun 12, 2015

chad said:
I would imagine a 30 amp fuse would suffice in that fusable link wire ?

I think a 30 would be too low. Probably would need a slow blow style also?

Jackpot50 · Jun 12, 2015

What gauge wire is going to bulkhead.
Check to see how much that size wire is rated and go 10 Amp under.

747mopar · Jun 12, 2015

Jackpot50 said:
What gauge wire is going to bulkhead.
Check to see how much that size wire is rated and go 10 Amp under.

You can't think like you do around household wiring where 12 gauge equals 20 amps, in automotive wiring the wires generally are better quality and because of the short runs can handle way more amps. Just take a look at the main feed on your car... pretty small for everything it runs.

Shorthorse · Jun 13, 2015

Found this on Allpar.com

Alternator output rating Wire gauge Fusible Link
Under 50 Ampere 12 16
50-65 A. 10 14
85 A. 8 12
100 - 120 A. 6 10

- - - Updated - - -

Lets try this again

HawkRod · Jun 13, 2015

So discussions have started about fuses vs. fusible links. That is fine, but you need to make sure you find the cause of the problem. It is NOT the fault of the fusible link - it did what it is designed to do and saved your car from burning down.

Your Alternator gauge is fed by battery power and is only protected by the fusible link. This is a red wire under the dash and it goes directly to the alternator gauge. The other side of the alternator gauge goes to your alternator (through the firewall) and also feeds your fuse panel. This is a black wire. I would start by checking those wires and see if something is shorting out.

Good luck

chad · Jun 13, 2015

Oh I have every intention of figuring out why the link burnt up. I Was just wondering if it was feasible to replace it with a fuse.

nm9stheham · Jun 13, 2015

It is certainly feasible. But both are fuses. The fusible link has the property of being more forgiving for transient overloads than regular fuses so that is why they got used as a main fuse. Wait a minute... the car chase in Bullitt is starting......

I keep hoping the Charger survives.....Oh well; that's Hollywood for you!

The 2 big bangs was probably the electrical system failing and the ignition cutting in and out as it failed; the bangs were a result of the ignition stopping, gasoline building in the exhaust for a moment, and then lighting off when the ignition fired up again a couple of time before it fully failed.

Do this to check for a short in the system:
Get a regular 100W incandescent light blub and get ready to connect it in series with the battery - lead to ground. With the doors closed and everything off, connect an 14 or 12 ga wire where the fusible link was installed. Connect up the light bulb; if you have a short in the electrical system, the light will glow but the bulb's resistance will keep the current low. If you get this glow, remove the bulb, then disconnect the 2 firewall plugs where the fusible link does NOT connect through and re-connect the bulb to see if the bulb still glows. If it does, the short is in the inside harness. (You can hook the bulb directly across the battery at the start to see how much the glow will be from a dead short.)

BTW, fusible links do fatigue and go out so that may be your only issue.

BTW#2; the wire on cars is small in those days because it was a cost thing. Copper in cars carries current no better or worse than in houses. But house wiring is set by the NEC (National Electrical Code) and has conservative factors involved since people burn to death due to bad house wiring. The consequences of failed car electronic is rarely as bad and there are no set standards, just cost and reliability tradeoffs.

747mopar · Jun 14, 2015

nm9stheham said:
It is certainly feasible. But both are fuses. The fusible link has the property of being more forgiving for transient overloads than regular fuses so that is why they got used as a main fuse. Wait a minute... the car chase in Bullitt is starting......

I keep hoping the Charger survives.....Oh well; that's Hollywood for you!

The 2 big bangs was probably the electrical system failing and the ignition cutting in and out as it failed; the bangs were a result of the ignition stopping, gasoline building in the exhaust for a moment, and then lighting off when the ignition fired up again a couple of time before it fully failed.

Do this to check for a short in the system:
Get a regular 100W incandescent light blub and get ready to connect it in series with the battery - lead to ground. With the doors closed and everything off, connect an 14 or 12 ga wire where the fusible link was installed. Connect up the light bulb; if you have a short in the electrical system, the light will glow but the bulb's resistance will keep the current low. If you get this glow, remove the bulb, then disconnect the 2 firewall plugs where the fusible link does NOT connect through and re-connect the bulb to see if the bulb still glows. If it does, the short is in the inside harness. (You can hook the bulb directly across the battery at the start to see how much the glow will be from a dead short.)

BTW, fusible links do fatigue and go out so that may be your only issue.

BTW#2; the wire on cars is small in those days because it was a cost thing. Copper in cars carries current no better or worse than in houses. But house wiring is set by the NEC (National Electrical Code) and has conservative factors involved since people burn to death due to bad house wiring. The consequences of failed car electronic is rarely as bad and there are no set standards, just cost and reliability tradeoffs.

A beg to differ! Actually the biggest difference is the length of the conductors, your comparing a home which will have runs of wire equaling 100s of feet compared to a 19' long car where most wires are less than 8 ft long. It's common knowledge the longer the run the more amps it robs just like people burning up their power tools on 100 ft extensions cords? Just trying to help one understand why smaller wires on a car have much heavier loads when compared to household wiring.

nm9stheham · Jun 14, 2015

Mmmmmm.....I'm an electrical engineer. No need to explain 'common knowledge' of electrical circuits and wiring ... LOL. The copper in house wiring and auto wiring is of similar grade and electrical properties, so the phrase 'better quality' makes no sense. But none of that helps the OP at all.

HawkRod · Jun 17, 2015

747mopar said:
Just trying to help one understand why smaller wires on a car have much heavier loads when compared to household wiring.

Don't confuse current and power. Remember that Power = Current x Voltage (P=I x V). So 10 amps at 12 volts = 120 Watts, and 1 amp at 120 volts = 120 Watts too. The power capability of any wire is the same.

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