Fusible link replaced w/ a 30-amp inline fuse?

[magg383]

I recently replaced the fusible link (near starter relay) w/ a 30-amp inline fuse since the fusible link fried because of some electrical issues that have now been repaired. (The inline fuse came attached w/ 12-gauge wire) I don't want to replace it w/ another stock fusible link in case of more electrical issues. If the fuse pops with an inline fuse, then I know there is another electrical issue vs. the fusible link. The car is a 73 Challenger w/ a 383, non-AC, w/ a 60-amp alternator.
My question is, is 30-amps a correct replacement for my application? If not, what fuse amperage should I be using?
Thanks for any input!

 

[Chryco Psycho]

You should be OK the only worry is the ammeter where all of the current is run through the guage , have you connected both wires to one terminal bypassing it ? Otherwise nothing through the firewall draws 30 amps , the circuits that do use relays , I suggest using relays for the headlights also as the lights will be brighter

 

[sixpactogo]

A 30A fuse is better than nothing but a fusible link is designed to take a spike in current flow and will actually take a larger than 30A spike but not for long. IMO, you would be better off with a 25 Amp circuit breaker than a fuse since a breaker can take a spike as well but will trip before burning up your wiring. I think all newer cars these days use a breaker instead of a fusible link.

 

[Katfish]

Doesn't the entire load run through the amp meter?
With the lights, and other stuff on, I'd think you'd need more than 30A.
But the good part is it will be easy to up the fuse if needed.

 

[Challenger RTA]

By chance did you do any work on the alternator? cycle the hi low beam switch?

 

[Challenger RTA]

The above information is good. The amp gauge wire would be a concern.
You have to ask yourself why did it blow? It very rarely blows unless it's a dead short.
Over time of others shorting it with short shorts can weaken the link.

When motor is not running power is supplied by battery. Travels from battery to bulkhead connector 16 to red wire A 12R to amp meter. Follow the blue and yellow dots. Then to 12Bk to splice one. This is where it feeds all the loads or circuits. The headlights are feed from splice 1 through the Black wire white tracer. Q3 12R One red wire from splice one feed the battery side of the fuse box. J1 12R The other red wire feeds the ignition sw. Follow yellow dots. The Black wire R6 12BK Blue dots comes from the alternator. It supplies power for the load and charging the battery. BE AWARE! When the key is not on there is power the alt terminal.

Splice one

 

[magg383]

By chance did you do any work on the alternator? cycle the hi low beam switch?

I replaced the alternator last yr. w/ a new one. What did you mean by "cycle the high low beam switch?" ?

 

[Challenger RTA]

Turn the high and low beams on and off. The foot switch and the the plug melt . Then it shorts out. That will blow the fuse able link.

 

[magg383]

Turn the high and low beams on and off. The foot switch and the the plug melt . Then it shorts out. That will blow the fuse able link.

I will take the foot switch off and inspect it. The last time I used it was a couple yrs. ago, but that's when I started having electrical issues, so who knows. Is this a very common problem? I'm also going to take the steering wheel off and check for any grounded-out ign. switch wires

 

[magg383]

A 30A fuse is better than nothing but a fusible link is designed to take a spike in current flow and will actually take a larger than 30A spike but not for long. IMO, you would be better off with a 25 Amp circuit breaker than a fuse since a breaker can take a spike as well but will trip before burning up your wiring. I think all newer cars these days use a breaker instead of a fusible link.

I didn't realize the advantage of the fusible link vs the inline fuse. I think I'm going to put a fusible link back in. What gauge of wire do they recommend for 73 e-bodies for a replacement fusible link, 14 or 16? I would think 14. Also, would you recommend a circuit breaker over a fusible link with my situation? Thanks!

 

[EW1BH27]

Just throwing this out there, there's also "slow blow" fuses. This following statement is from a Google search.
The time-delay, or "slow blow", fuses were developed for situations where acceptable momentary overloads are encountered, such as starting a motor. As the name implies, this type of fuse will carry an overload several times the normal load for a short period of time without blowing.

 

[sixpactogo]

I didn't realize the advantage of the fusible link vs the inline fuse. I think I'm going to put a fusible link back in. What gauge of wire do they recommend for 73 e-bodies for a replacement fusible link, 14 or 16? I would think 14. Also, would you recommend a circuit breaker over a fusible link with my situation? Thanks!

Don't quote me on this but I believe the fusible link used a 16 gauge wire in most cases. It was a cheap charlie method used rather than a circuit breaker since it served the purpose. They always installed them near the battery since that is where the source of current flow and the first to overheat from high amperage. The main difference between the fusible link and a circuit breaker is the link is a one time thing and a breaker can be reset. The fusible link is cheap and easy. You could make your own with a short piece of 16 gauge wire fused to a 12 gauge wire like the factory did. Here is a pic of my 68 Charger wiring diagram showing the link from the battery to the firewall plug protecting the wiring in the cabin in case of a short. It is a combination made up of a #12 wire and #16 wire.

 

[magg383]

Just throwing this out there, there's also "slow blow" fuses. This following statement is from a Google search.
The time-delay, or "slow blow", fuses were developed for situations where acceptable momentary overloads are encountered, such as starting a motor. As the name implies, this type of fuse will carry an overload several times the normal load for a short period of time without blowing.

That is very interesting and good info. That might explain why my 30-amp inline fuse just recently popped right after starting my motor. Would you have a recommendation on what amperage that would be acceptable for my car for one of these "slow blow" fusses?

 

[magg383]

Don't quote me on this but I believe the fusible link used a 16 gauge wire in most cases. It was a cheap charlie method used rather than a circuit breaker since it served the purpose. They always installed them near the battery since that is where the source of current flow and the first to overheat from high amperage. The main difference between the fusible link and a circuit breaker is the link is a one time thing and a breaker can be reset. The fusible link is cheap and easy. You could make your own with a short piece of 16 gauge wire fused to a 12 gauge wire like the factory did. Here is a pic of my 68 Charger wiring diagram showing the link from the battery to the firewall plug protecting the wiring in the cabin in case of a short. It is a combination made up of a #12 wire and #16 wire.

View attachment 126727

Thanks for the good feedback. Sound like a circuit breaker is superior to a fusible link. Check out what EW1BH27 found out about slow blow fuses. That also sounds like a great option. Your thoughts?? Thanks!

 

[EW1BH27]

I don't want to make a recommendation BUT here's an interesting read.

Raso Tech - Everything you need to know about Fusible Links

A blown fusible link can leave you stranded on the highway without warning. Discover how to ensure your electrical system is protected.

www.raso.name

In his first chart it shows a 16 gauge fusible link would carry a maximum of 22 amps. I'm concerned with you blowing a 30A after start-up. The guy in the article didn't have that issue with a 30.

Scanning the article, I pasted where the author wrote this....
I tried a 20 amp ATC fuse (salvaged from a wreck during an earlier quest for parts) but, after a long cold-weather cranking session, it blew shortly after my car started while I was warming up the engine. I replaced it with a 30 amp ATO fuse and I've had no fuse issues so far.

 

[sixpactogo]

Thanks for the good feedback. Sound like a circuit breaker is superior to a fusible link. Check out what EW1BH27 found out about slow blow fuses. That also sounds like a great option. Your thoughts?? Thanks!

IMO, a fusible link is a slow blow fuse. Just a cheaper one. A circuit breaker is superior to a fusible link because it can be reset and reused where a fusible link has a one time use just like an inline fuse. If you are still blowing that 30A fuse you have in place of the fusible link, you still have a short somewhere. I recommend you get an ohm meter and start checking for grounds on every circuit until you find it. Or have an electrician help you out.

 

[EW1BH27]

Just because........

https://www.amazon.com/Amp-Slo-Blo-MDL-Fuse-Volt/dp/B01NBHPR54

 

[MoparCarGuy]

I would highly recommend purchasing an actual fusible link wire if you go that route. The insulation on a fusible link is unique. Making your own fusible link from a certain gauge wire with unknown insulation properties is hazardous.
Summit Racing has a variety of fusible link sizes in stock. Powermaster is a reputable brand and supplier.

The rule for sizing a fusible link is four (4) sizes smaller (numerically larger gauge size) than the protected circuit’s wire size. The alternator (ALT) feed is the wire gauge used to size the fusible link.
Examples:
Main is 14 then fusible link is 18
Main is 10 then fusible link is 14

Many of us have upgraded our alternators to 100 Amp and increased the main feed wire to 6 AWG with a corresponding 10 AWG fusible link. The 6 AWG bypasses the factory ammeter and goes to the starter relay’s main stud with the inline fusible link of course. Some on the forum are proponents of keeping the ammeter (if you are knowledgeable enough to know the limitations) while others consider bypassing it mandatory and replacing the ammeter gauge with a voltmeter. Both views are valid with good mechanical/electrical knowledge.

Read this thread for some insight on this issue: LINK

 

[72RoadRunnerGTX]

Many of us have upgraded our alternators to 100 Amp and increased the main feed wire to 6 AWG with a corresponding 10 AWG fusible link. The 6 AWG bypasses the factory ammeter and goes to the starter relay’s main stud with the inline fusible link of course. Some on the forum are proponents of keeping the ammeter (if you are knowledgeable enough to know the limitations) while others consider bypassing it mandatory and replacing the ammeter gauge with a voltmeter. Both views are valid with good mechanical/electrical knowledge.

Curious about why those promoting the alternator to battery by-pass wire don’t seem to be concerned with the resulting increased overcurrent potential the by-pass exposes to the original unfused stock wiring. Adding this additional 6ga wire run with a 10ga fusible link, paralleling the stock charge path and stock 16ga fusible link, bring the total over-current protection for the stock unfused 12 ga wiring to something closer to 60-70 amps. Should a short occur anywhere in the stock unfused wiring there would be two paths for current to flow from the battery. The stock 16 ga fusible link will not open as designed.

 

[MoparCarGuy]

Curious about why those promoting the alternator to battery by-pass wire don’t seem to be concerned with the resulting increased overcurrent potential the by-pass exposes to the original unfused stock wiring. Adding this additional 6ga wire run with a 10ga fusible link, paralleling the stock charge path and stock 16ga fusible link, bring the total over-current protection for the stock unfused 12 ga wiring to something closer to 60-70 amps. Should a short occur anywhere in the stock unfused wiring there would be two paths for current to flow from the battery. The stock 16 ga fusible link will not open as designed.

@72RoadRunnerGTX has cautioned forum members many times about making changes to the factory wiring without the proper electrical knowledge. His point about a unintended parallel path is valid and points out that you MUST abandon the original ALT feed to the bulkhead connector>ammeter>bulkhead connector>starter relay IF you want to properly bypass the ammeter and the problematic bulkhead connector connections.