replacing fusible links

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fishy68

fishy68

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Trying to help a buddy repair his wiring harness for his 1990 Dodge Ram and it has a multi fusible link arrangement (5 total all molded into one outlet) and one is burned up. I know a lot about wiring but I don't know why they use fusible links instead of fuses. Can anybody tell me if a fuse (standard or slow blow type) is an acceptable substitute for the fusible link? The wire leading to and from the fusible links are 10 gauge. I know 10 gauge wire is rated at 30 amps continuous so would a 30 amp fuse be ok to use?
 
I know on newer cars they used MAXI fuses to replace the older links. As far as the proper size you may want to pm slantsixdan as I remember a link he posted a while back with a reference to sizing the fuses to replacing links. I know links could handle the small spikes without popping and I would think the MAXI rating would be a bit higher than the continuous amp rating. Johnny.
 
I have eliminated fusable links before without a hitch.....then again i am no expert on the exact science of what the perfect match would be.

normally when I had done something liek that I would find what the wire ran to and powered and I would replace it with a fuse that I thought was suitable for the type of power drain would be put on the wire that was used to run whatever it was connected too.

I have also used breaker fuse's (cool down fuse) so if for some reason there was a voltage spike....it would kick the breaker before causing problems and then you could just reset it and have another go.

but more often than not ....if there is a spike in voltage high enough to kick it than there is probably a fault in the electrical and you would be better off using a regular old fuse.

I dont "think" you should have any problem using a regular fuse though.
 
Thanks for the input guys. I kinda figured the fusible links will take spikes better than a regular fuse so I was thinking of using slow-blow type fuses. I have an ammeter so I can run a current test and see what they spike at and operate at so I think I'll be ok.

Thanks again, Tracy
 
years ago i swapped an efi 4.0 in place of a carbed 2.8 in a Ford Ranger. I used resettable circuit brakers instead of fuses. to be safe, i used ones that i knew were underated as a starting point. fuel pump was rated for, say a 15 amp draw, i put a 10 amp breaker on it. i never had a breaker trip. put a maxi fuse on the charge line, rated 15 amps under the charge lines capacity, it never popped niether. i know slant six dan is not a fan of the madelectric guy, but on his site he talks about the sizing of fusible links. might not hurt to at least call they guy and talk to him about putting fuses in place of the links. if you call, be warned, the guy LOVES to talk...please post any info you get from either one of them.....
 
I figured on doing the same, using small fuses to start with to be safe. I'll check out SlantsixDan's site and see what I find out. Thanks
 
Thanks for the link Matton. How did yours work out? I already wired in a 6 pole fuse block to replace the fusible links this afternoon so there's no turning back now. I'm going to do a load test and use slow blow fuses a little smaller than what it pulls and see what happens.

Only one thing I can't agree with Slantsixdan on is how he says a crimp fitting is better than soldering. I have been a mechanic for nearly 30 yrs. and have done it both ways. Crimp connectors are a short term fix IMO. Soldering (if done properly) not only makes a better electrical connection but it moisture proof's the connection to a degree. Using shrink wrap over it seals it up for good. I have never once had a failed solder connection but I sure have seen a lot of corroded crimp connections, even ones that were only a couple yrs. old. A high quality crimper does do much better but it still doesn't seal the connection at all.
 
I'm going to do it tomorrow.
I decided to stick with the fusible link as it is not as hard to find as I originally thought, plus I have a really great harness that I do not want to hack up. I will also ditch the ammeter wire set up, either by bypassing it or just hooking the wires together.
Solder and shrink wrap will probably win out for me as well.
Per Dan's posts, I installed the bosch headlamps and H4 bulbs already, just waiting for the relays, and the better bulbs all around- what a difference!
 
matthon said:
I'm going to do it tomorrow.
I decided to stick with the fusible link as it is not as hard to find as I originally thought, plus I have a really great harness that I do not want to hack up. I will also ditch the ammeter wire set up, either by bypassing it or just hooking the wires together.
Solder and shrink wrap will probably win out for me as well.
Per Dan's posts, I installed the bosch headlamps and H4 bulbs already, just waiting for the relays, and the better bulbs all around- what a difference!
Click to expand...

Gotcha. If this one I'm repairing didn't have a weird fusible link setup where 5 go into one molded connector I'd do the same. Those headlamps do make a nice diff. I put them in my Cuda and now I can actually see what's in front of me at night. I didn't even do the relay mod since I totally rebuilt my original harness and upgraded the wiring. I think it'd still benefit from the relay's. Maybe someday I'll get time to do the conversion.
 
Fusible links can be placed most anywhere without concequence. Blade type fuses will need to be in a safe place. Water, debrie, etc.. is conductive. Thats why newer vehicles have a fancy enclosure strategicly placed to house their maxifuses.
 
never had any luck with crimp connectors. just not very weather resistant.....
 
RedFish said:
Fusible links can be placed most anywhere without concequence. Blade type fuses will need to be in a safe place. Water, debrie, etc.. is conductive. Thats why newer vehicles have a fancy enclosure strategicly placed to house their maxifuses.
Click to expand...

Good point. I picked up a real nifty 6 pole blade type fuse holder at NAPA and have that wired in. It'll be going on the left fenderwell (inside the engine compartment) up high near where the finder bolts to the inner fender so I think it'll be out of the way of any water splashing. But to be safe we'll make a cover for it.

inkjunkie said:
never had any luck with crimp connectors. just not very weather resistant.....
Click to expand...

Yep, same luck here. I use them for something temporary but that's it.
 
matthon said:
I'm going to do it tomorrow.
I decided to stick with the fusible link as it is not as hard to find as I originally thought, plus I have a really great harness that I do not want to hack up. I will also ditch the ammeter wire set up, either by bypassing it or just hooking the wires together.
Solder and shrink wrap will probably win out for me as well.
Per Dan's posts, I installed the bosch headlamps and H4 bulbs already, just waiting for the relays, and the better bulbs all around- what a difference!
Click to expand...

Where did you end up getting your fusible link? I just blew mine on the Dart Wagon.
 
Fuselinks are not just wire-shaped fuses. They behave differently, and that needs to be taken into account if you go changing the circuit protection setup. Take a look at this post and the links from it (and the posts above and below it in the thread), for info on replacing fuselinks with other types of circuit protection devices if that is what you intend to do.
 
slantsixdan said:
Fuselinks are not just wire-shaped fuses.

I figured as much. I noticed in your post you mentioned it was a cost effective way to do things therefore fuses should work fine if properly sized.
Click to expand...
They behave differently, and that needs to be taken into account if you go changing the circuit protection setup. Take a look at this post and the links from it (and the posts above and below it in the thread), for info on replacing fuselinks with other types of circuit protection devices if that is what you intend to do.
Click to expand...

Thanks for the link and info. I am always overly cautious when it comes to wiring because I realize the risk of fire. The thing that surprises me is according to the table in the link it shows using a much much higher rated maxi fuse than what you'd think.

I had figured on starting with fuses rated much lower than that. For instance 12 gauge wire is rated at handling 20 amps yet in this table it shows the ignition feed wire feed using 12 gauge wire (with a 18 ga. fusible link) being replaced with a 50 amp maxi fuse. That's 2-1/2 times the wires rated limit. I had figured on starting with fuses rated lower than the wires limit.

We got the truck running and today I'm going over to run load tests on all the circuits and size the fuses accordingly. I have an ammeter with a min/max register so I figured on loading the circuit with what should be the max load and use a fuse just slightly smaller (taking into account the load limit of the wire size of course) than what the meter shows and see how it works.
 
fishy68 said:
Trying to help a buddy repair his wiring harness for his 1990 Dodge Ram and it has a multi fusible link arrangement (5 total all molded into one outlet) and one is burned up. I know a lot about wiring but I don't know why they use fusible links instead of fuses. Can anybody tell me if a fuse (standard or slow blow type) is an acceptable substitute for the fusible link? The wire leading to and from the fusible links are 10 gauge. I know 10 gauge wire is rated at 30 amps continuous so would a 30 amp fuse be ok to use?
Click to expand...
Do not use fuses. Fusible link uses heat to work, it melts, hard fuses will not duplicate that.
 
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