What size fuse between battery and alternator?

[Synyster06Gates]

When I replaced my alternator last night I ended up blowing the fusible link so I had to re wire it. I'm using 4 gauge wire with a 100 amp fuse at the moment. Will the 100 amp fuse be enough or do I need to get a bigger one? Driving around it seemed okay but I never went above 4000 rpms. I have the shaker 1000 and a 135 amp alternator. I was thinking about getting a 150 amp fuse.

Thanks!

 

[Redfire281]

I would have thought that the fuse should be something less than the max output of the alternator. In other words if my alternator was rated at 135 amps, I would want the fuse to blow at possibly 125 amps in order to protect the electronics from the alternator going haywire and overcharging. I could be wrong.

 

[Synyster06Gates]

That's kinda what I was thinking, but at the same time 4 gauge wire has a maximum rating of 135 amps for chassis wiring and 60 amps for power transmission, so anything sustained above that would melt the wire. Ford was using 6 gauge with a 10 gauge fusible link so I assume that wouldn't take any more than 100 amps.

 

[05stroker]

I use 125a on mine no issues.

 

[Synyster06Gates]

In that case I'm gonna run the 100 as long as I can so I don't have to buy a new fuse holder. Hopefully it works!

 

[ummduh]

In that case you'd be fusing the wire to protect the wiring, not the alt. The fuse also goes closest to the battery. I'd use a 4ga wire and a 150A fuse on that.

 

[Synyster06Gates]

In that case you'd be fusing the wire to protect the wiring, not the alt. The fuse also goes closest to the battery. I'd use a 4ga wire and a 150A fuse on that.

Correct, I am doing it to protect the battery. The fuse is about 3'' away from the post.

 

[michael.konor]

My schematics show that the part is an 8GA Fusible Link.

 

[Synyster06Gates]

My schematics show that the part is an 8GA Fusible Link.

Does anyone happen to know how many amps that can take before blowing? Hopefully below 100A

 

[ummduh]

Why so worried about fusible links? Ditch them and go to a fuse setup.

I use these :
http://www.waytekwire.com/item/46039/HIGH-AMP-AMG-FUSE-HOLDER/

And then order 2 or 3 fuses, one to install and a couple to keep as spares in the glove box. Just the Ford offroader in me, I am never without a spare of whatever can leave me stranded.. Like a spare tfi back in the day. Or a spare duraspark.. Back in the day.

Fusible links are a fpita.

 

[Synyster06Gates]

Yeah I did go to a fused setup, but I only have a MAXI fuse holder for the time being and was wondering if 100A would be enough

 

[05stroker]

Yeah I did go to a fused setup, but I only have a MAXI fuse holder for the time being and was wondering if 100A would be enough

You can get a 125a MAXI at Napa.

 

[RocketcarX]

100 would prolly work, until the starter starts to drag a little or you add compression, I would think. If you pop it move up 25 amps in fuse size and go from there.

 

[ummduh]

What would the starter dragging or high compression have to do with the amperage the alternator puts out?

You'll be fine with a 100a fuse until you draw more than 100A from the alt.. I may be wrong, but don't all these cars have 135a alts? Or is that just a h/o option with the mach 1000 stereo?

I'd carry a spare or two. But I always do anyways.

 

[Synyster06Gates]

My stock one was 135A, so is the one I just got. What would cause me to draw 100+ amps? I have no idea how much power the car draws.

 

[onehotpny]

What are you fusing any way? for a larger amp for audio or something else? a fuse is just like a breaker on a house, meaning it's to protect your electrical system, if you put to big of a rated fuse in, it won't protect what you have.. fuses are made to blow if there's a short or fault or even if there's a bad ground.

 

[Synyster06Gates]

From the factory there is a fusible link between the battery and alternator to protect ALL of your electronics in case the alternator fucks up/grounds out and tries to send too much power to the battery.

 

[ummduh]

Well add up all the stuff drawing power and figure on worst case.

Wipers on high- 15a
Blower motor on high - 10a
Radiator fan on high - 30a
Headlights - 5a
Fog lights - 5a
Stereo - 5A for a standard, 15a+ for mach 1000
Rear window defogger - 10a
Fuel Pump - 15a?

105a right there. Are you always (ever?) going to have that much going on? Ya never know. The blower motor on high running the defogger kicks on the a/c which kicks on the radiator fan. So cold misty night with all your shit really. Or worst yet a cold winter morning!

Well you get the point. There's still a shit ton of stuff drawing power. You still have your ignition system, ecu, miscellaneous lights and motors throughout the car.
Some of my values are probably not exactly right but they're in the ballpark.

If I were you I'd carry a spare fuse and order a 150A setup asap. But that's just me, I actually like wiring work. Not a paid professional at it but I've learned a lot the hard way.

 

[05stroker]

I feel like I have wasted my time here. The 125 works period. I have a 1k amp and a .5k amp on my system and all. 125a is all you need.

 

[ummduh]

Perhaps, but 150 is more appropriate for a 4g wire. I'm not concerned with the output of the alt being less than that, Imo the fuse in this case is merely to protect the wire against a dead short.