All, i purchased a 1966 Plymojuth Valiant a year ago. after i had it a week, it died. upon investigation, the fusible link had been replaced with an inline fuse. this had blown. after fiddling with it and changing it multiple times, i did some work; replaced battery, alternator, voltage regulator, ballast resistor, coil. i also added a body ground, and after it sat over the winter, it worked for a month. my kid drove it one day and left it at a buddys house. battery drew dowd, jumped it, and it started. drove it home and fuse blew again. inline fuse holder melted. so i put in a 25amp water tight blade fuse. drove it 2 miles and parked. left an hour later and drove home. tried to restart and nothing (fuse had blown). it seems that the fuse predominantly blows when shutting the car off. now a fusible link is essentially a time delay fuse, while the fuse is instantaneous, correct? my questions are 1) what should i use in place of the fusible link, 2) any thoughts on why it blows when shutting the engine off? any help would be greatly appreciated!! Joe
1966 Valiant Fusible Link
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Welcome to the forum. You need to isolate where the short is that is making the fusible link blow. There is some kind of draw in a circuit that runs off the direct power, like the door lights and brake lights, head lights. Something is feeding back after the car is shutting down, so it is really a matter of finding out where the draw is coming and repairing it. Although you have changed all the electical components, the short could be anywhere from the amp gauge itself, the ignition switch, or the constant power items mentioned. A broken wire shorting out, scraping, or pinched is most likely the location. You could try to diagnose by removing the fuses, starting and then stopping the car, make sure your fuse is good, install one fuse at a time, which could alleviate the fused circuits, then start tracing wires for the constant power items. This also explains the dead battery, power draw is constant at some location it isn't supposed to be.
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And you are correct, a fusible link is a time-delay fuse, whereas the discrete fuses in cars are fast-blow. You can try putting in a slow-blow fuse, but as stated, there appears to be a short that must be fixed first. And you need to put the proper amperage fuse in place of the link.
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When attempting to use a fuse in place of a fusible link on these older single-fuselink 40-to 60 amp alternator cars, 25 amps is not near enough. If i wanted to, and i have for testing, i would use a 30 amp fuse at a minimum, preferrably a 35 or 40 amp fuse(uncommon in some places, but not rare as you might think). the main reason a smaller fuse will blow is the initial charge the alternator will attempt to put in the battery to quickly bring it up above 14 volts as soon as the engine starts.
for diagnostics and/or if non-oem components are of no concern, i would use a maxi-fuse holder and start with a 50 amp fuse, perhaps using a 60 amp(no higher!). unless you opt to give someone a jump using your car or you get a jump with your own battery dead, this maxi fuse will work quite nicely. it will blow instantly if someone tries to give you a jump with reverse polarity, or a major fault to ground occurs somewhere. it can quickly be replaced, and you just might like it.
for the longest lasting and most rugged solution, once you have vetted the electrical system in your car and you are done tinkering, go back to the fuselink. use a 5" long piece of 16 gauge hypalon insulated wire for this purpose. (on a related note, when selecting fuselinks, they will always be 2 guage sizes smaller than the wires they protect, which on almost all 60's big 3 models, would be 12 guage wire.) with the fuselink back in, you can give/get jumpstarts, run all your accessories with the engine off, and have happier diodes in your alternator due to lower resistance to the battery.
The factory fuselink is a tad shorter, whick makes it a bigger fuse, but i like em a bit longer so they "blow" a bit easier if a fault should occur. but for some, the fuselink should be 2" long if they have bigger alternators/fans/amps/batteries/lights/etc./etc.
for diagnostics and/or if non-oem components are of no concern, i would use a maxi-fuse holder and start with a 50 amp fuse, perhaps using a 60 amp(no higher!). unless you opt to give someone a jump using your car or you get a jump with your own battery dead, this maxi fuse will work quite nicely. it will blow instantly if someone tries to give you a jump with reverse polarity, or a major fault to ground occurs somewhere. it can quickly be replaced, and you just might like it.
for the longest lasting and most rugged solution, once you have vetted the electrical system in your car and you are done tinkering, go back to the fuselink. use a 5" long piece of 16 gauge hypalon insulated wire for this purpose. (on a related note, when selecting fuselinks, they will always be 2 guage sizes smaller than the wires they protect, which on almost all 60's big 3 models, would be 12 guage wire.) with the fuselink back in, you can give/get jumpstarts, run all your accessories with the engine off, and have happier diodes in your alternator due to lower resistance to the battery.
The factory fuselink is a tad shorter, whick makes it a bigger fuse, but i like em a bit longer so they "blow" a bit easier if a fault should occur. but for some, the fuselink should be 2" long if they have bigger alternators/fans/amps/batteries/lights/etc./etc.
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