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  #1  
Old 01-03-2019, 05:37 PM
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rang-a-stang rang-a-stang is offline
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What size inline fuse should I use for main power?

As I am re-wiring my rig, I replaced my ammeter with a volt meter and am adding another set of fuses under my hood to power things like electric fans, headlights, etc.

I now have all my power going into the cab for the stock stuff (radio, heater, brake lights, Horns, etc.) via the fat red wire, that is tied (electrically) to the same point as the alternator output, starter solenoid, and battery Positive terminal. The yellow wire is also connected to the same point but no longer feeds the red wire or where the ammeter was; The fat yellow line will now power a separate bus bar and relays for new items in the cab (CB, brake controller, stereo amp, seat heaters, etc.) like the paper drawing in post #31 here:
http://www.ifsja.org/forums/vb/showthread.php?t=160450

They mention 40 amp breakers. That seems kind of low. Is that correct? Then again, I moved headlights, off road lights, and all my new stuff to relays that do not draw current from that Red line... (they have their own line/fuse). hmmmm....
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  #2  
Old 01-04-2019, 08:14 AM
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Depends on the gauge of the wire and alternator output.
There are charts online for wire size/max amps if you undersize wire bad things like meltdowns or fires can occur.
If a fuse is too small it'll constantly blow, if it's too big the meltdown/fire hazard comes back in.
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  #3  
Old 01-04-2019, 11:53 AM
wiley-moeracing wiley-moeracing is offline
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I am running a mega fuse off the alt and battery of 125, but have a lot of electrical power coming off a high power alt. It then branches out to smaller inline fuses per circuit.
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  #4  
Old 01-04-2019, 01:06 PM
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Have you put a meter inline to see what your actual draw is? 40a might be enough.
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  #5  
Old 01-04-2019, 01:42 PM
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Woodchomper Woodchomper is offline
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See pics below of what my son and I did on his '81 J10. We also put another fuse panel on the driver's side fender to house headlight & fog light relays and various fuses. The passenger fuse box has relays for the fuel pump and cooling fan. Forgive the wiring mess as these pics were taken before loom was installed.





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  #6  
Old 01-04-2019, 08:48 PM
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rang-a-stang rang-a-stang is offline
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Thanks, everyone.

I have not metered it. I put a 50 amp fuse on one line and 40 on the other. If I blow either of those, I think I have bigger problems. I am not real confident in those wires to carry much more than that so I guess I'll run them up a flag pole and see if they fly.

Woodchomper, that's an amazing looking fender well!
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  #7  
Old 01-05-2019, 06:35 AM
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iapexl8r iapexl8r is offline
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you might have a look here, lots of good info.
https://www.wirebarn.com/Wire-Calculator-_ep_41.html


http://bdfuses.com/fusesnwires.php
Keep up the good work
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  #8  
Old 01-06-2019, 06:17 PM
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bkilby bkilby is offline
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Quote:
Originally Posted by Woodchomper
See pics below of what my son and I did on his '81 J10. We also put another fuse panel on the driver's side fender to house headlight & fog light relays and various fuses. The passenger fuse box has relays for the fuel pump and cooling fan. Forgive the wiring mess as these pics were taken before loom was installed.



Nice wiring job.
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  #9  
Old 01-06-2019, 08:47 PM
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hey,does anyone here know how to.......
 
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Forgive the mess .....LOL nice job

really Rich?????

any better and you should be wiring up NASA equipment- but whats up with the fuse that looks like its 180 out from the rest of them ...lose a point for that...

Steve
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  #10  
Old 01-06-2019, 09:47 PM
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asphaltrockdweller asphaltrockdweller is offline
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hey Rang I sent some pictures to your .mil email account with what I did a while back.
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  #11  
Old 01-07-2019, 02:05 PM
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Woodchomper Woodchomper is offline
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Rang-a-stang...I think you would be better off using circuit breakers (30A-40A) instead of a fuse for your main wiring. I also like using a 100A or so mega fuse for the alternator (assuming you have upgraded the alternator). The nice thing about a circuit breaker is that it will reset once an over-current condition is removed. This could be the difference of making it home or not.



By running a 50A fuse you may melt your wiring before the fuse blows.
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  #12  
Old 01-07-2019, 03:07 PM
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asphaltrockdweller asphaltrockdweller is offline
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One of my favorite "Old School Memebers" here wrote up why ANL fuses were good for our old Jeeps, and that they were a great replacement for inline fuseable links.

Just search some of Joe Guilbeau great post on wiring.
wish he was still around here, as I loved reading his posts.
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  #13  
Old 01-07-2019, 03:19 PM
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So what I ended up doing was a straight 1ga wire from the 150amp CS144 to my battery + Terminal (red arrow in picture). There is another 1ga wire from my + terminal straight to my starter solenoid (Yellow arrow in the picture). Lastly, there is a ~6ga wire from my battery + terminal over to a new fuse block on my driver fender well (green arrow in my picture). From that fuse block, I have a 40 amp fuse going to my stock wiring (the ~10ga red wire going into the cab). There is another fuse that feeds that yellow ~10ga wire and that goes into the cab and will feed another bus bar that will feed my new interior accessories (CB, brake controller, stereo amp, etc.). I am running my fan relay through the fuse block on my fender, the headlight relays, off-road light relays, EFI Computer, etc. That way the only real power going in through the firewall goes in via the ~10ga stock wires (red and yellow that used to feed the Ammeter) and is limited to relay switching and light loads.

Don't worry, the embossed tape is temporary and the wires are not secured yet, but they will be once everything is wired up, works, and is ready to hit the road.

Advice? This is work in progress so I am not too proud to accept advice and change.

iapexl8r, those links are great! I have been reading them over and over. Dusty, I'll be at my desk tomorrow and will check out your pictures.


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  #14  
Old 01-07-2019, 04:45 PM
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Woodchomper Woodchomper is offline
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Rang-a-stang...Your setup looks good. I never had the guts to run a straight thick wire from the alternator to the battery. Others have done it but they do not have my luck. Anyway here is a link for you if you decide you want to replace your 40A fuses with circuit breakers: https://www.delcity.net/store/Maxi-F...p_152.h_187702
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  #15  
Old 01-07-2019, 05:59 PM
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Cecil14 Cecil14 is offline
 
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FWIW, the factory OBD1 XJs had 2x 30A fuses (60A total) between the alternator and the battery. And that was the only thing that ran off the alternator.


aa
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Old 01-16-2019, 10:00 AM
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In my J20, converted to voltmeter, the alternator wire goes directly to the battery. I inserted a fusible link in both it and the wire that goes to the rest of the car. Personally I think a fuse (as an "upgrade" from a properly sized fusible link) is pointless for this application. The fusible link(s) is(are) meant to protect the car from the stored energy in the battery, in case of catastrophe like a wreck. Their main advantage is they are super-reliable, because the are hard-wired into the circuits. No moving parts (circuit breakers), no mechanical contacts (fuses). They should never be needed, short of a catastrophe.


This was covered in the latest ammeter bypass thread, if you are interested - http://www.ifsja.org/forums/vb/showthread.php?t=184885
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  #17  
Old 01-16-2019, 09:41 PM
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I always try keep things simple-ish. Alternator wire is single fusible link on the positive cable from LS style truck. The TBI is stock GM sealed relays & fuses.
Headlights are on a single breaker & 2 GM sealed relays.

Since it is an 88 though better setup stock vs. 79 stuff.
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  #18  
Old 02-01-2019, 03:14 PM
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Probesport Probesport is offline
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I dropped a small relay and fuse box right behind my battery, was cheap on Amazon and it cleans up a lot of circuits.







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  #19  
Old 08-29-2019, 05:13 AM
DustyW DustyW is offline
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Hey probesport, you have a link on that fuse block. I like the look of that.
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