Where to put Fusable Link

Joined
Jan 23, 2003
Messages
187
Location
San Jose, CA
Hi All,
I got very little left of a wiring harness in my 1971 FJ40 (it was a high school project rig) and it didn't have a fusable link. Thoughts of me buring up made me go get an 8 gauge Maxi-Fuse link that I put in at the battery with a 50A fuse. Is this the correct spot? Funny thing is that I pulled the fuse out while it was running and it still ran. Must still be charging the alternator. Seems like such a circuit with a fusable link ought to make everything shut down.

Soooo do I
a) Leave it where it is and all is OK
b) Move it after the alternator so all current from the batt/alt go through the link
c) Get another Maxi-Fuse and put it in the alternator circuit

I'm thinking if there is any short circuit in the system the fuse will still blow if it pulls enough amps to max the alternator out + 50A for the fuse. I just hope it blows though and the wiring is indeeed protected.

Thanks for your input,
Scott
 
Joined
Jan 23, 2003
Messages
187
Location
San Jose, CA
andrewfarmer said:
Two links.
one to all wiring except alt
2nd near alt on fat wire.
This covers both current sources.
Ok, so I'm running a 50A on the battery circuit. What do I need on the alternator circuit? Is 50A enough? BTW: I'm not running a high output alternator.

Thanks, Scott
 

Pin_Head

 
 
 
Joined
Feb 6, 2002
Messages
14,911
Location
OC, CA
It would depend on how it is wired and what type of alternator you have.

You always need a fusible link between the chassis (large white wire with blue stripe) and the battery. 50A may be on the light side, but I don't know what the original value is.
If your alternator is wired through the stock amp meter (large white wire), you don't need another fusible link, but it is not a bad idea. (At least Toyota didn't use an additional fusible link at the alternator until the late 70s or 80s) Later cruisers have a fused alternator.

If you are running an alternator with an output greater than 50 amps, you should not run it through the stock amp meter. You should either upgrade the stock wiring to handle the higher output or wire the altermator output directly to the battery through an appropriate size link. The amp meter will only read chassis current if you wire the alternator dirctly to the battery, but this is no big deal if you have a volt meter.
 
Joined
Jul 18, 2005
Messages
799
Location
Wellington, NZ
I'm pretty sure OEM is 30amps - 50 will be plenty given the alternator is on the other side of it (= very little current draw off battery while engine running)

If you're bolting the fusible link to your battery, it's handy to bolt a spare on at the same time in case it blows - make the spare a size bigger :)
 
Joined
Jan 23, 2003
Messages
187
Location
San Jose, CA
What do you think an early 70's chevy (no A/C) alternator puts out? 40-60A?

I'm not running an Amp gauge. The + wire from the batt is spliced into the hot lead for the alternator so where the Maxi-Fues is right now only protects against draw from the battery. I currently have a 50A fuse in it. I suppose I ought to put another Maxi-Fuse on the alternator circuit too but what amp fuse should I use. Suppose something at least as great as the alterntor rating.

Scott
 
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