Fusible link elimination

I'm in the process of yet another re-wire on the Jeep, and this time I'd like to eliminate the fusible links that come off of the power distribution solenoid. I'm assuming I need some sort of thermally tripped circuit breaker. The question is, how do I size the breaker? Is there a simple formula for the length of the fusible link and it's guage size to help me size an appropriate breaker?

These guys have teh breakers i want to use:

http://www.bussauto.com/products/circprot/

And the fuse panels to put them in:

http://www.bussauto.com/pdf/15600.pdf

CRASH said:

I'm in the process of yet another re-wire on the Jeep, and this time I'd like to eliminate the fusible links that come off of the power distribution solenoid. I'm assuming I need some sort of thermally tripped circuit breaker. The question is, how do I size the breaker? Is there a simple formula for the length of the fusible link and it's guage size to help me size an appropriate breaker?

Click to expand...

I somehow don't believe that the length of the thing matters, it's more related to wire gage.

I've been halfheartedly digging around on this meself - something for me to do in earnest this summer, while I'm not in classes (I need a break...) I've never been happy with fusible links, I don't know why.

If you do happen to dig anything up independently, do please let me know - so I can see if I can verify it, or just have a basis to bash my own numbers out. I don't think you can use regular "ampacity" ratings on fusible link wire, since it's DESIGNED to overheat and blow out BEFORE the rest of the circuit...

5-90

Handy page, lists appropriate breaker/fuse sizes.

Guage/colors match 91 FSM.

Consider running a length of good wire from the alternator to a marine fuse block, then from it, a couple shorter lengths to the battery(ies?) and to the PDC. The post on the PDC doesn't get more happy with many huge cable terminals involved.

http://www.westmarine.com/webapp/wc...ga fuse holder/All_2/mode+matchallpartial/0/0

http://www.westmarine.com/webapp/wc...eSea Mega fuse/All_2/mode+matchallpartial/0/0

I have a couple spare/unused 175a megafuses if anyone needs them. Free for postage.

i used the hiamp resetable breaker on mine, and relocated the battery to the back to make room for another a/c compressor for compressed air
ill install it when i run across one fab some brackets and go to town

put the breaker as close to the battery as possible,max 9inches

Some of those wires looked undersized based on the values of that site. Factoring the crappy wire OEM's use I would set them that high.

Personally I wouldn't do a breaker in all those apps. They can be a real PITA to trouble shoot and sometimes need to be disconnected to reset. I still like the standar ATO style fuse. I've had several problems with the maxi style fuses blowing at way over the rated value. They large spades on them seem to desperse heat really well which causes them to blow slower. I kind of follow a 60 amp minimum but still would rather use a AGU in those apps.

The general rule I always followed when working on OEM wiring.
10 ga - 30 amp
12 ga - 25 amp
14 ga - 20 amp
16 ga - 15 amp

Pretty conservative but I very seldom have any kind of problem.

The style of blocks I like are on this page starting about 1/4 down.
http://www.americanautowire.com/products/Fuse_Panels_Blocks_and_Accessories.cfm

http://www.wranglernw.com carries a large selection of different bank blocks with either single inputs or seperate inputs.

I use the ones in the bottom left for alternators and anything over 100 amps.

Funny, while I was out looking at those fuseable links I finally found the one I had been having a problem with.

Isn't the whole point of the fusible link to burn slowly, unlike a fuse? I thought a breaker accomplished this, i.e. it could take a spike without blowing, unlike a fuse. Maybe I'm wrong and could just use fuses for this app???

Lincoln said:

Some of those wires looked undersized based on the values of that site. Factoring the crappy wire OEM's use I would set them that high.

Personally I wouldn't do a breaker in all those apps. They can be a real PITA to trouble shoot and sometimes need to be disconnected to reset. I still like the standar ATO style fuse. I've had several problems with the maxi style fuses blowing at way over the rated value. They large spades on them seem to desperse heat really well which causes them to blow slower. I kind of follow a 60 amp minimum but still would rather use a AGU in those apps.

The general rule I always followed when working on OEM wiring.
10 ga - 30 amp
12 ga - 25 amp
14 ga - 20 amp
16 ga - 15 amp

Pretty conservative but I very seldom have any kind of problem.

The style of blocks I like are on this page starting about 1/4 down.
http://www.americanautowire.com/products/Fuse_Panels_Blocks_and_Accessories.cfm

http://www.wranglernw.com carries a large selection of different bank blocks with either single inputs or seperate inputs.

I use the ones in the bottom left for alternators and anything over 100 amps.

Funny, while I was out looking at those fuseable links I finally found the one I had been having a problem with.

Click to expand...

I've got a 94 underhood PDC that I've metered out and have the wiring figured on. It's on my list of things to graft into the wiring of my renix rig. I too want to ditch the fusible links, since one left me stranded.
My basic plan is to use the PDC maxi fuses and run those back to the original circuits. Going to beef the PDC mains wire so I can also use the PDC fuses under the hood for an upgraded light harness, aux lights, CB's, anything I want fused close to the battery. it's got relay holders, so I'll be switching my relays to it also.
That's the plan anyway.
PDC cost me 24 bucks with all the fuses in it at the JY.

87manche said:

I've got a 94 underhood PDC that I've metered out and have the wiring figured on. It's on my list of things to graft into the wiring of my renix rig. I too want to ditch the fusible links, since one left me stranded.
My basic plan is to use the PDC maxi fuses and run those back to the original circuits. Going to beef the PDC mains wire so I can also use the PDC fuses under the hood for an upgraded light harness, aux lights, CB's, anything I want fused close to the battery. it's got relay holders, so I'll be switching my relays to it also.
That's the plan anyway.
PDC cost me 24 bucks with all the fuses in it at the JY.

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This is a very good idea. Bravo.

CRASH said:

This is a very good idea. Bravo.

Click to expand...

Thanks.
now I just gotta get it finished.
Sucks to do major upgrades to your DD

87manche said:

Thanks.
now I just gotta get it finished.
Sucks to do major upgrades to your DD

Click to expand...

Now, can you get replacement terminal ends that accept new wire and plug into the bottom of the PDC? That way, you wouldn't have to do a bunch of splices........

CRASH said:

Now, can you get replacement terminal ends that accept new wire and plug into the bottom of the PDC? That way, you wouldn't have to do a bunch of splices........

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That's an excellent idea! I hadn't thought of that, and was just going to solder them all in place. I don't know if the existing harness will be long enough though.
The only other problem I can see is that the PDC is pretty well assembled, and I don't know about taking it apart to get at the underside of the sockets. I'm sure it could be done, but I hadn't looked into it because I never thought of that.
If anything it will be a lot easier to solder extensions with connectors on them, rather than soldering a big wire loom mess together in a tight space.

Most of these kinds of circuits come apart with the appropriate tool. For instance, GM Weather-Pak connectors use a couple of sizes of small tube, slip over the terminal end, push down, and the wire and terminal come out the back of the connector. Buy a bulk male/female WP terminal set from summit, and you can put your WP's anywhere on the wiring you need to. Pretty cheap, too: http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM-900495&N=115&autoview=sku

I'll look into it. Leaving to go NC wheeling the end of the week. I was going to do the wiring first week of september. THat's the next 3 day weekend. Always nice to have that third day in case something doesn't go as planned.

CRASH said:

Isn't the whole point of the fusible link to burn slowly, unlike a fuse? I thought a breaker accomplished this, i.e. it could take a spike without blowing, unlike a fuse. Maybe I'm wrong and could just use fuses for this app???

Click to expand...

I think the whole point of the fusible link is it saved them a peny or two. Notice how the quit using them. Also most repair manuals have them replaced with an inline fuse.

Look at them items they run. None of them need a slow trip. The one that's been out for a while on mine was the stock wire for the electric fan. I got tired of looking for which one and just hooked up my own relay. Last night I found the wire melted (insulation still there) about 2" from the fusible link.

I'll use breakers in high amp apps, but I have had two that didn't trip on a short. Normally the breakers tend to be more sensitive (require less of a short to trip) but I stopped trusting them after the two and went to ANL fuses.

Solder is your friend. Do them right. There should be enough wire there to hook them up to the style of block I posted above. No splicing. If you do splice, solder and shrink them. It makes life a whole lot better later.

Oh, trust me, I stocked up on solder and and shrink tube before I started the cage re-work, knowing that the Renix wiring mess was going to have to be re-done (again). I think the PDC from a later model is a great idea, and cheap to boot.

Lincoln said:

I think the whole point of the fusible link is it saved them a peny or two. Notice how the quit using them. Also most repair manuals have them replaced with an inline fuse.

Look at them items they run. None of them need a slow trip. The one that's been out for a while on mine was the stock wire for the electric fan. I got tired of looking for which one and just hooked up my own relay. Last night I found the wire melted (insulation still there) about 2" from the fusible link.

I'll use breakers in high amp apps, but I have had two that didn't trip on a short. Normally the breakers tend to be more sensitive (require less of a short to trip) but I stopped trusting them after the two and went to ANL fuses.

Solder is your friend. Do them right. There should be enough wire there to hook them up to the style of block I posted above. No splicing. If you do splice, solder and shrink them. It makes life a whole lot better later.

Click to expand...

Crash, I used this tech write-up when I upgraded my charging/electrical system.

http://www.olypen.com/craigh/charge.htm

I used 1/0 welding wire for the main leads and a Mega fuse to replace the fuseable link. I started out with a 100 AMP fuse, but went to a 150 AMP fuse when I installing a Hellroaring dual battery system due to their suggestion. Good Luck

Woody

Wa Woody said:

Crash, I used this tech write-up when I upgraded my charging/electrical system.

http://www.olypen.com/craigh/charge.htm

I used 1/0 welding wire for the main leads and a Mega fuse to replace the fuseable link. I started out with a 100 AMP fuse, but went to a 150 AMP fuse when I installing a Hellroaring dual battery system due to their suggestion. Good Luck

Woody

Click to expand...

Thanks for that as well.

I did some more digging. I might as well fix some of the issues with mine while putting in the new alternator and welder. I noticed that several of the wires are getting pretty soft which make me think they won't last an overly long time.

This is a pretty good picture of the style of block I'll probably use. Wranger has them (catalogue is a little old) in everything from 1 in 3 out to 12 in 12 out. They say the will also do others. I'll have to verify the size but it looks like a 6 circuit is 1.687" wide x 3" long. The 12 ciruit is 1.687" X 5.625". I'll figure out the mounting but it looks like two sixes may fit the best. I counted 9 leads coming out of the links. I'll figure out the sizes when putting in the fuses.

I figured a few more to handle my acc stuff. I do have an old 4 spot AGC type mounted on the drives side though so maybe a 9 to handle the factory stuff and then move all of the ACC items to a new block where the 4 is.



This is a good chart to give you an idea on what amperage of protection. Keep in mind that this is for a high quality wire that I have never found in a parts store. The 16 ga is a tin coated 29 strand wire. It doesn't break down nearly as quick as the factory stuff. That is why I always fuse conservatively:


And here is an explination of the breaker types. The style you mentioned can either be a Type 1 or Type 2. Which would explain why I had problems trouble shooting them in the past.