Fusible Link Replacment

rodrju

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Hello:

Unfortunately my drive the other evening ended with the Diplomat being towed the remaining 1.5 miles to the house.

A blown fusible link caused the engine to die and a rather large backfire that managed to take out the entire muffler.

The fusible link in question is on the left front wheelhouse. (See photos) and is part of a group of links the combine into one.

The one that blew obvious has something to do with ignition—as I do not even have crank with out it.

Also unfortunate, it burned so completely that no wire exists where it entered the factory plastic splice.

So:

1) Replacement options

Must I replace it with fusible link—or I can replace with an inline fuse?

2) I believe I found what MAY have caused it to blow—a spade connector wire that use to run the carb kicker that I had taped up was touching the firewall.

Any other thoughts on why this could have happened ?

What would be the best way to replace?

This car does have a lean burn conversion to conventional Mopar electric ignition.

Thanks

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If you find that wasn`t the short that caused your blown link then I would check the ignition switch connector at the the base of the steering column. Many times they melt and short out and cause problems like yours. I would replace with a fuse link if possible. Also make sure you use the correct size link wire when replacing . My understanding is a standard fuse won`t work well. Some people have used a slow burn in place but I have never tried one. I have seen fuse links for sale on ebay so you may want to check there if you can`t find any locally.
 
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You can try a fuse but they used to use fusible link because they don't blow like fuses with quick spikes. Oddly they make the fusible links harder to replace like that. You can get them at Napa and some other part stores.
 
Okay, I'll ask the question cause I don't know the answer.

Why would you need to accommodate quick spikes? Doesn't that inherently mean that the wiring itself or some place in front of a 'connector' you should have something (I'm sure there is some electrical term that's appropriate here) to filter or 'clean' the current so you don't have spikes?

Completely ignorant of what's really going on here.

JW
 
I guess better wording is short times of higher load. Same sort of reason why slow blow fuses exist in normal electrical applications.

A fuse would normally go before those fusible links so it should usually be some sort of short before the wiring gets to the fuse box.
 
These spikes (alternator on-off is a huge problem due to massive residual energy in it when turned off by the regulator) can only be rectified with lots of electronics shit, nothing cheaply available at the mid-ages our beloved cars have been built.

The alternator-regulator does not really regulate - it just turns it on and off at specific voltages...

Still today, every electronic component in a car has to protect itself - there's still no guarantee for nicely regulated 12 volts in a car.
 
Spikes in cars come from the alternators themselves, or regulators, or can come from various electrical motors and heavy electrical loads (for example high power car stereo amplifiers) switching on an off. When a heavy electrical load switches off, it can cause the voltage in the car to temporarily spike higher because the regulator can't adjust fast enough (it has been regulating the voltage based on a heavy load, now that the load is gone, usually the voltage goes up). This is the opposite of what happens when a load becomes heavier; the. voltage usually drops (sags) Until the regulator commands more power from the alternator. The same goes for things like air conditioning condensers, and in addition, the motor itself can actually put voltage spikes back into the car's electrical system (this is called an inductive spike or kickback). All of the electrical parts in the car must be made to withstand this, or they will fail. Part of the protection scheme for cars is the fuse/circuit breaker/fusible link array that will open up if the spike is too high, or lasts too long.

There are a number of parts that can be used to reduce spikes, things like MOVs, Transorbs, or in extreme cases, gas discharge tubes, but they can only take a relatively small number of spikes before they stop working or even burn out. This is not true for gas discharge tubes, but they are not suitable for use in an automotive environment because they won't stand up to the vibration that is in common in cars.
 
I replaced my fusible links with Maxi fuses. There are Cartridge Fusible links out there, Chrysler used them in the 90s. They could be adapted into our cars easily. LH cars used them (Intrepid, etc)
 
I was able to find the likely culprit—some melted insulation on a wire that I should have routed better. Upset with myself for being careless.

Was able to replace the fusible link and we are running again. Only driven about 20 miles or so but all seems well.

I did what I could to repair it as close to factory.

I have always felt the electrical system on the Diplomat—as well as my Duster—is weak. I’ve replaced the cables, alternator, voltage regulator—keep getting inconsistent performance from the charging system. Considering going to the 100 amp setup or the later denso setup if I can find the brackets.
 
Problem with a stronger alternator is, that the problem of weak wires only shows when either (or both) the battery is not near full (higher amperage go to battery) or more load is added (e.g. high wattage radio, more lamps, electric fan, fridge.. ).
 
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