Technical Painless Wiring Warning

This is how I would do it...

Appropriately sized battery cable from battery to starter.

#4 AWG wire from alternator to starter with 100 amp MIDI fuse mounted in between like so...



and a 100 amp MIDI fuse like this...


...between battery or starter terminal and fuse panel with #8 AWG feeding the fuse and two #10 AWG from the fuse feeding the fuse panel (if it requires two feeders) or a single #8 AWG feeding the fuse panel.

I can draw it up for you if that's too confusing and I also offer all the parts mentioned. Let me know if I can help!

 

Please.

 

Please explain how these protect the wire and under what conditions.... Be specific.

 

Is any of this to protect the equipment, or just the wires?

 

X3

 

Why fuse the wire between the alternator output and the starter terminal? What happens if that fuse blows/opens? Is the wire on either side of the fuse no longer hot? What happens with the alternator if that fuse blows?

 

Since Mr48chev posted a link I took a peek at all 148 pages. I’ll just say that if no one ever did wiring or knew the factory way the car was wired they’d be lost. On one page they call said wire one thing then call it another else where. Oh, this is the best! Early into it it say’s not to cut away any wire/wires not needed. Then further down near the end it say’s to cut this wire away.
So in the end, yes Steve there is fault. But as alway’s wiring isn’t for everyone so expect the calls and threads to keep coming.

 

Used a Coach Controls kit for the coupe and will be using the same one on my 56 build. Vastly superior product in every way. This is how they are powering the panel in their kit. No shortcuts!

 

I keep looking at the underhood junction block/fuse panels on my Powerstroke and Exploder, and the PS especially is a very robust unit with small fuses, large fuses and breakers. All the trailer wiring goes thru there, and there would seem to be plenty of circuits to run anything one would need in a car. Wiring harnesses going to the panels are also pretty robust. Seems like they would be a good start for a new harness? Some stuff is run thru the "inside" panels, probably adaptable

 

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have to agree - --- Never heard of Coach Controls --sure that there are other brands that people have had good results with, and full do it yourself installs - - biggest thing is that most every ride has it's own quirks and can not duplicate 100% what someone else has done -- plus, a whole lot depends on experience of installer -- my first experience for complete rewire was of a Hot Rod left for dead -- did some good creative stuff, did some stupid stuff like using only one color wire thru out

 

This kit has the same fault, the output from the alternator is fused. All this is doing is adding a potential problem, it is not protecting anything. With that kit you need to eliminate the first 100 amp fuse, and then you need to run the alternator output all the way to the starter solenoid terminal.

 

Isn't that where the automakers put the fusible links? Must do it for a reason.

Years ago I had an old Ford RV. Long story short, I was crossing Nevada with the 12v fridge going and stereo blasting. Flicked on the A/C and very soon the idiot light came on and smoke started pouring out the doghouse. Managed to make it to an exit. The power wire from the alternator fried, original wiring. I managed to replace it with some lamp cord and carry on, hot, thirsty and quietly.

 

I went though all those pages too and have too say that that I would far prefer that you could disconnect any unneeded wires at the fuse block.

They are spendy in comparison to Painless but one thing I always liked about the Ron Francis fuse blocks is that you connect each wire to the fuse block yourself one at a time. A bit more work and for some a bit more clutter but you don't cut wires you just don't connect them in the first place.

 

The fuse blows before the wire is overloaded. Condition? Voltage regulator fails, ground short in the harness, etc.

Both. The fuse in the alternator wire protects the entire system if the voltage regulator fails, etc. The fuse between the battery and the fuse panel protects the entire system.

To protect the system if the voltage regulator fails. Consider modern alternators that can produce upwards of 200 amps. That's alot for a 10 AWG wire to handle if something goes awry. If the fuse blows, the rest of the system is protected. Yes. Nothing.

That is not a fault. It protects the entire system from a potential amperage overload resulting from an alternator failure. A fuse in the alternator circuit is industry standard.

 

American Autowire and Coach Controls offer kits similar to this as well. FYI

 

The harness!

The equipment provides the draw, so generally it's particular circuit is not feeding anything until it is switched on.
If [for example] you had a short circuit in a heater motor, it would blow its respective fuse when switched on. [the short can draw a greater load than the wire feeding it]

Generally the main feed from the battery to the starter is unprotected because it is a relatively small distance [and the starter solenoid is the "circuit breaker" between the motor and batt] but the take-off from the solenoid to the harness should be fused.

When people do the "fashion show trend" of placing the battery in the trunk, they really should use a Ford starter relay on this circuit [mounted close to the batt] and a separate fused main feed to the harness.

I've seen a major fire caused by a battery in the trunk conversion on an RX7 race car. The homemade lightened flywheel grenaded and took out the main starter feed wire [and fuel line] that went down the frame rail.

When you start understanding about "draw" [or load] instead of "feed" [or supply] with wiring, it makes more sense.
Think of your house..........there is an 8 megawatt power station supplying a 4w LED bathroom light



This controversial harness [below] is in reality quite clever


The battery draw while recharging is limited to 40a [480w] after cranking the engine because of the 8g wire
And this is fuse protected both directions [shown as a maxi-fuse]

But the Alt can supply 2 x 30a [720w] via the 960 and the 915/915 combined
so if the battery is drawing 480w recharging there is a surplus supply of 240w to run the vehicle.

If the draw of running the vehicle is maxxed out at 720w [eg A/C , sub-amps stereo , headlights etc etc] it can be supplied via 915 and the 960/916 combo
So the path of electricity on the 916 wire can change direction [depending on demand]

If the car drawing 720w [max] off all the accessories, this leaves no surplus to recharge the battery.
90% of the time the Alt is just keeping the battery "topped up" and also running the accessories at the same time.

If you wanted to improve the max draw from the alt , then use the Hotrodder's "More's Law" approach by increasing the size of the 960 wire [which isn't needed]

 

Yes, but there is a difference between using a fusible link at the starter terminal, and remote mounting a fuse. If the fusible link blows, the line is dead, period. If the inline fuse blows both sides of the wire remain hot. The inline fuse adds at least 3 potential failure points, both cable connections to the fuse and the fuse itself. And I do recall at least one post here on the HAMB of a member who had an inline fuse fail on him, at night, miles from home. He was able to troubleshoot it and bypass it and make it home, but the point is, it does add a potential failure point.

 

Wrong. If there is a failure in continuity between the alt output and the battery, such as a disconnection between either cable end at the fuse, or at the fuse itself, it is the equivalent of disconnecting the battery. If this happens when the engine is running it can cause a very high voltage spike that can damage any other components in the system; as well as damage the diodes in the alternator.

Done using a fusible link at the starter terminal. Not the same thing as remotely mounting an inline fuse.

 

Ahhhh, this is key to understanding electricity. Current is always drawn, it's not pushed; due to a difference in potential (voltage) between 2 points. The current will only flow to fill the difference in potential. You're right, once you get that it all starts to make more sense.

 

Here are a couple ways it's being done in the industry...

https://www.painlessperformance.com/wc/drawings/alternators/Battery Power - Midi Fuse Schematic.pdf

https://www.americanautowire.com/media/productattachments/files/downloads/92972151 510475 IN 0.0.pdf

American Autowire recently changed their kits over from using fusible links and now use the fused setup. When one fails (blows) the result is the same, but a fuse is easier to replace than a fusible link. That's after one diagnoses the issue.

 

Lots of slating of at least one brand in this thread, has anyone actually contacted these guys to suggest what is in their product is 'wrong'?

 

Hey, if wiring wasn't scary enough, now we get graded on it. Yikes!
(Probably just me, but, it sounded funnier in my mind,).

 

The fusible link doesn't have multiple potential sources of failure. The inline fuse does. Nuts holding the cables to the fuse vibrate loose; corrosion builds between the cable ends and the fuse terminals, the fuse itself can loose continuity to the holder. These things can and do happen, no matter how remote you might say it is. The point is, you're inserting a potential point of failure into the system, and I'm not sure the protection the fuse offers (in the case of a regulator failure that causes the alternator to go to full output) exceeds the potential for failure it introduces. Maybe a better solution is to size the output of the alternator and the wire between the alternator output and the starter terminal more appropriately to the needs of the installation.

 

Isn’t all this 200 trillion amp mega talk over rated when the cars on this sight need only 30 to 55 amp?

 

That's what I'm thinking....

 

The fusible link itself is the failure. One little melted wire failure leaving you stranded if/when it fails/trips unless you carry wire strippers, crimpers, and an extra fusible link. And that's****uming the fusible link, during its literal meltdown didn't damage anything else.

What part of the 4AWG wire that I posted seem inappropriate to the application and how does increasing the size protect the circuit from failure? Using your logic, a 21 circuit fuse panel must have hundreds of points of failure. It's a wonder these cars even run at all!

Johhny, what is your alternator rated at for peak amps? That's what you need to build to. And the fact that they can fail and "runaway" can lead to component damage. It's not the 30 amps that the system specs out at, it's the alternator's spec and the risk of damge if something fails and the output spikes.

 

Any connection. Spliced. Soldered or clamped is a source for potential failure . Excluding battery main cables , every circuit needs a fuse/ fusible link .

 

Blues, I always thought that electricy was “ pushed” from one side of the battery to the other with voltage. And that the appliance in between the positive and negative regulated how much current passed. I have always heard how much current something “ draws”, but I always thought that was along the lines of slang, kinda like the term “ suction” in the flow of liquids. I have always considered voltage to be “ electric pressure “ . In my brain , trained with water flow, I cannot understand electricy being “ drawn” . Maybe a little help here?







Bones

 

Not to be a hypocrite, I'll be adding something a little high zoot to my 39, a 600w amp and 2 10" subs. However that will go in with it's own power and source protection by design. The Powergen will keep up when I crank up the tunes, and should not tax the car much at all if any. I like simple.