RF Harness - Fusing

[jengum]

I have read that fusing the alternator output is a good practice and not to fuse the battery to starter connection for a front mounted battery.

What about the 2 power supplies to the RF fuse box (battery side) and the ignition switch that feeds the RF fuse box (accessory & ignition sides) & headlight switch? Does anyone fuse these 2 power supplies and if so how did you go about it? Is this overkill for something that may be a low probability event of shorting out?

I ask the question because my plan is to add a switched aux fuse block for some add on circuits and most of the aftermarket fuse block suppliers show a recommended master fuse upstream of the fuse box in their schematics.

[mrglaeser]

I have fused the charge cable on other projects, but only because it had a lot of draw and I upgraded to a heavier gauge cable. I got a mega-fuse which has worked well. For the Roadster I didn't do this myself - but it wouldn't hurt.

On the power supply to the fuse box, I think that might be redundant. The circuit(s) causing any issues should blow fuses long before the power circuit would be in trouble. At least that is my opinion. I personally would run a new power line for the additional fuse box.

[Presdough]

Make sure your fuse is rated at or near the capability of the alternator. I have seen a number of Chrysler products with an 80 amp fuse on a 120 amp alternator. If you kill the battery and jump start it you will blow the fuse...

[edwardb]

I have fused the charge cable on other projects, but only because it had a lot of draw and I upgraded to a heavier gauge cable. I got a mega-fuse which has worked well. For the Roadster I didn't do this myself - but it wouldn't hurt.

On the power supply to the fuse box, I think that might be redundant. The circuit(s) causing any issues should blow fuses long before the power circuit would be in trouble. At least that is my opinion. I personally would run a new power line for the additional fuse box.

X2. Properly rate mega fuse on the alternator charge wire is good practice. Not mandatory but doesn't hurt anything. No fuse on the starter feed. Your RF harness has fuses on each circuit so no need to fuse the input voltage. If you add another fuse box, each of those circuits should be properly fused.

[BrewCityCobra]

I have read that fusing the alternator output is a good practice and not to fuse the battery to starter connection for a front mounted battery.

What about the 2 power supplies to the RF fuse box (battery side) and the ignition switch that feeds the RF fuse box (accessory & ignition sides) & headlight switch? Does anyone fuse these 2 power supplies and if so how did you go about it? Is this overkill for something that may be a low probability event of shorting out?

I ask the question because my plan is to add a switched aux fuse block for some add on circuits and most of the aftermarket fuse block suppliers show a recommended master fuse upstream of the fuse box in their schematics.

I struggled with this exact same issue during my build. It is certainly easy to go crazy contemplating "perfect" circuit protection upstream of the fuse block but I am yet to see a build where that has actually been employed. Strategic weakness I suppose.

It seems like many will leave the starter cable unprotected (relying on the size of the cable and short run to the starter as a form of protection), and will wire the fuse block feed without protection (which is what RF dictates). No real way around that without putting two or more circuit breakers right next to your battery.

Like you said, a popular form of protection is to add to a circuit breaker on the alternator feed. This is one that I felt was worth the price of admission.

To the extent it is helpful, I included a link to my build thread that has a schematic of how I wired my "upstream" circuits. The circuit includes a cutoff switch, alternator circuit breaker, and leaves the starter wire unprotected. For a bit of reference, the "buss bar" in the schematic is the point where my main fuse block, auxiliary fuse block, and a few other accessories are powered from.

https://thefactoryfiveforum.com/showthread.php?38979-The-Brew-City-Cobra-427W-IRS-Putting-the-Color-Down&p=482433&viewfull=1#post482433