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#1195722 - 03/12/12 12:23 PM Fusible link volt/amp specification limits?
peelerboy Offline
master

Registered: 01/19/03
Posts: 9830
Loc: Detroit, Michigan, USA!
Hey guys! Does anyone know what the technical limits of a fusible link are? More specifically, for my 1971 Challenger 383 car.

What exactly is it that will eventually burn the fusible link out in my car? I'm looking for a number... how many amps?... how many volts? What's the breaking point spec? Anyone know?


Dale

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#1195723 - 03/12/12 12:33 PM Re: Fusible link volt/amp specification limits? [Re: peelerboy]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 27017
Loc: Balt. Md
Dale where the heck have you been ? There is different sizes that the factory uses. Basically the fuse link is a smaller piece of wire then the circuit is so it will burn out first in case of a short before the larger wire in the rest of the circuit. I have never seen exact #'s on the amout of amps it takes to burn them out. But I would guess that a 20 gauge fuse link will only take about 30 amps. The heater circuit uses a larger one like 16 or 14 gauge as they can draw 25 amps on high speed so I would think about 40 or a tad more amps would burn it out. Course when you get a dead short it will pump alot of amps thru it and burn out real fast. Ron


Edited by 383man (03/12/12 12:34 PM)
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My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#1195724 - 03/12/12 12:49 PM Re: Fusible link volt/amp specification limits? [Re: 383man]
peelerboy Offline
master

Registered: 01/19/03
Posts: 9830
Loc: Detroit, Michigan, USA!
Quote:

Dale where the heck have you been ? There is different sizes that the factory uses. Basically the fuse link is a smaller piece of wire then the circuit is so it will burn out first in case of a short before the larger wire in the rest of the circuit. I have never seen exact #'s on the amout of amps it takes to burn them out. But I would guess that a 20 gauge fuse link will only take about 30 amps. The heater circuit uses a larger one like 16 or 14 gauge as they can draw 25 amps on high speed so I would think about 40 or a tad more amps would burn it out. Course when you get a dead short it will pump alot of amps thru it and burn out real fast. Ron




Howdy, Ron!

I've just been busy working like crazy and raising a family. Haven't had the time to mess around with the cars too much, but things are finally letting up a little and I'm back in the garage. I actually took the Challenger out yesterday and made a couple beat passes. That was nice.


Thanks for the great response. The fusible link that should be in the harness connected to my starter relay... isn't! I know I can just go buy a little blue wire from Year One for $20, but I was contemplating putting in a durable fuse holder instead. Then I realized that I had no idea how much current it took to burn that wire out. I had one go on my `68 Road Runner a few decades back and had a tough time rigging something so I could get home again. Just thought I might modernize that one safety feature of my harness for easier serviceability.

Dale

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#1195725 - 03/12/12 01:22 PM Re: Fusible link volt/amp specification limits? [Re: peelerboy]
stumpy Online   content


Registered: 01/19/03
Posts: 29723
Loc: Grand Prairie,Texas
Problem with trying to replace a fusible link with a fuse is that links are slow blow so they can deal with the draw of a starter or the heater motor starting up. A fuse blows instantly with a high amperage draw and won't take the heavy initial spike.

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#1195726 - 03/12/12 02:35 PM Re: Fusible link volt/amp specification limits? [Re: stumpy]
a12rag Offline
top fuel

Registered: 04/23/07
Posts: 2183
Loc: Calgary, Alberta Canada
Fuses can be had in two types, fast acting and time delay. The time delay allows the fuse to ride through the high current draw (for a specified amount of time), yet will operate fast enough to protect during short circuits.

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#1195727 - 03/12/12 02:40 PM Re: Fusible link volt/amp specification limits? [Re: a12rag]
RapidRobert Offline
Circle Track

Registered: 11/20/03
Posts: 34510
Loc: Lincoln Nebraska
Unless you do some research & get the correct fuse (slow blow)I'm assuming or circuit breaker I'd keep it simple & replace your missing one w one from NAPA or the "help" rack at your parts house
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live every 24 hour block of time like it's your last day on earth

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#1195728 - 03/12/12 03:01 PM Re: Fusible link volt/amp specification limits? [Re: RapidRobert]
MY340 Offline
master

Registered: 01/20/03
Posts: 5270
Loc: Missouri
I'm using a 25A fuse & holder in my Duster which works fine.
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1970 FE5 Duster 360/904/3.91's SOLD 1973 TB3 SpaceDuster 340/4spd/4.10's SOLD Moparless for now but when the opportunity is right I'll have another one.

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#1195729 - 03/12/12 03:11 PM Re: Fusible link volt/amp specification limits? [Re: MY340]
RapidRobert Offline
Circle Track

Registered: 11/20/03
Posts: 34510
Loc: Lincoln Nebraska
Quote:

I'm using a 25A fuse & holder in my Duster which works fine.


That's good to know, might try it. I've always thought that a FL would still pass enough current to do damage before it blew as it did once on a '66 dart
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live every 24 hour block of time like it's your last day on earth

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#1195730 - 03/12/12 08:48 PM Re: Fusible link volt/amp specification limits? [Re: RapidRobert]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 27017
Loc: Balt. Md
All the newer cars use the real large type fuses in the PDC that take the place of the old fuseable link wire. Ron
_________________________
My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#1195731 - 03/12/12 09:11 PM Re: Fusible link volt/amp specification limits? [Re: 383man]
stumpy Online   content


Registered: 01/19/03
Posts: 29723
Loc: Grand Prairie,Texas
The new cars aren't turning over high compression v8s and running high draw heater motors etc.

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#1195732 - 03/12/12 09:29 PM Re: Fusible link volt/amp specification limits? [Re: stumpy]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 27017
Loc: Balt. Md
Quote:

The new cars aren't turning over high compression v8s and running high draw heater motors etc.




They are running heater motors that draw 25 amps and the electric fan draws a good bit on high. Its just that they do it that way now so its easy to replace them. And the starter draw has nothing to do with the fuseable link. Ron
_________________________
My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#1195733 - 03/12/12 10:43 PM Re: Fusible link volt/amp specification limits? [Re: 383man]
ahy Offline
master

Registered: 01/22/07
Posts: 7643
Loc: IN
The general guideline is to size the fusible link 2 wire sizes less than the main wire... 12 guage wire would use a 16 guage fusible link for example.

One sizing consideration is alternator output... a '71 would likley have had a 50 or max 60 amp alternator and a 12 guage charge wire. The 12 guage wire + 16 guage fusible link could be considered OK for intermittant current up to 50 or 60 amps so that would be the fuse size. Call it 60 amps. Continuous capability is more like 30 amps which is why muscle MOPAR's charge circuit wiring is weak.

All that said, with a stock system, you could spend $5 at Autozone for a length of 16 (or 14) guage fusible link and fit it in. Unless you are going to bypass the kinda weak stock system, that's that I'd do.

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#1195734 - 03/13/12 11:00 AM Re: Fusible link volt/amp specification limits? [Re: ahy]
peelerboy Offline
master

Registered: 01/19/03
Posts: 9830
Loc: Detroit, Michigan, USA!
Quote:

The general guideline is to size the fusible link 2 wire sizes less than the main wire... 12 guage wire would use a 16 guage fusible link for example.

One sizing consideration is alternator output... a '71 would likley have had a 50 or max 60 amp alternator and a 12 guage charge wire. The 12 guage wire + 16 guage fusible link could be considered OK for intermittant current up to 50 or 60 amps so that would be the fuse size. Call it 60 amps. Continuous capability is more like 30 amps which is why muscle MOPAR's charge circuit wiring is weak.

All that said, with a stock system, you could spend $5 at Autozone for a length of 16 (or 14) guage fusible link and fit it in. Unless you are going to bypass the kinda weak stock system, that's that I'd do.




Great stuff! Thanks for all these very informative replies, guys!

Dale

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