Engine Bay Fuse Remove/Replace

[neRok]

Tidying up the engine bay and I think I know what is going on, just want some confirmation. Ive studied the RHD 260z wiring diagram and believe the following is happening.

 

Battery connects to the starter, and the starter goes to one of the 2 fuses in the engine bay (white wire).

From that fuse (call it the big one), power goes to the shunt (white wire).

From the shunt, the wire (white+red) breaks off into a few places.

1 - To/from alternator (and to charge the battery, power must go backwards through the big fuse?)

2 - To the small engine bay fuse, which then goes to the ignition switch

3 - A wire that powers the top-right fuses of the internal fuse block and the passing relay

4 - A wire that goes to the combo switch and then powers the headlight fuses when lights are on (the top-left fuses of internal fuse block).

 

My query is that I do not think the small engine bay fuse is required. The 3rd and 4th wires run considerable distance without fuses, so I cant see a reason for the 2nd to have one so early (there will be fuses later). The big fuse will blow and isolate the battery if there is a problem in the wiring between it and any of the 'secondary' fuses. The alternator is always powering a considerable amount of wire anway, so I cant see this being any more of a problem either.

 

Opinions?

[Zedman240®]

Its important to have fusible links as close to the supply as possible as when a wire melts and the weakest link is further away, that melting wire will take out all the others in the loom making one big molten mess with a fire thrown in for fun. I've had to repair a few looms and it aint much fun.

[neRok]

Yer, but the fact that 2/3 are un-fused in the engine bay seems a bit silly.

[neRok]

Well I have gone ahead and done it. I purchased a fuse/distribution block, which has 1 stud 'input' and I got one with 6 fuse 'outputs' (come in 8, 10, etc). I haven't mounted it yet, but think I will on the 'side wall' between the brake booster and the window washer bottle.

 

The thick wire from the starter to the shunt goes to the stud, to provide battery power.

 

I put in a new wire from the alternator to the stud. I did not reuse the old alternator wire as there were a lot of connections along it and it went from engine to fender and around, whereas I rewired to firewall and around. I did not connect the alternator to a fuse, as the fuse block said 25amp max per fuse, and the alternator could put out 65+ (mines actually a 120 amper!)

 

Speaking of which, I un-taped the engine bay loom and removed all the coil, oil+water sensors etc. I will run these from firewall to engine too, for a cleaner look. I also removed the few 'useless connectors' from the factory wiring diagram and removed all the external regulator wiring as I have put an internal reg alt on. I will be drilling a hole in the 'side-wall' and run the light wiring through the wheel well, so the only wires in the engine bay will run along the firewall.

 

There were 2 thick white+red wires from the shunt/alternator/stock-fuse wiring that ran into the cab. These got connected to a fuse each, and that was it. Everything turned on as expected, but I havent tested the load of a running car with high-beams etc on yet. Depending on which circuit everything is on, it may overload one of the fuses. If that happens, I will run relays for the headlights to relieve the load, and this will probably work better anyway.

 

There were about 6 other pieces of thick wire that got removed. They connected shunt to fuses, alternator to fuses, etc. I got rid of the shunt, which means the amp meter wont work. I did this on purpose, because I put in a voltmeter that I pulled from my 76 260z (this is going into a 75). I chose the voltmeter because it has a charge light, which is necessary for the alternator I have chosen (a 2 wire bosch). If you wanted to clean up your stock engine bay in a similar fashion, you would connect the starter to the shunt, and the shunt to the stud. The stock wire from starter to fuse is already quite long, so there is no 'disadvantage' if you dont fuse the new starter to shunt wire.

 

I also have 4 spare battery voltage fuses now too, which is handy. With relays, I can easily wire in thermo fans, elec water pump, etc. Too easy!