Technical Rebel Wire Harness diagrams and wiring info

I have a charge wire kit from Vintage Auto Garage that came with 10ga wire and 125a inline fuse that I plan to use.

 

Do what you want. You asked if it would be safe. In my opinion, a 10 ga that long will be undersized and could overheat. Perhaps I am reading more length into your deal than is there. I use an 8ga on mine for a shorter run.

Ben

 

You could also run it down the left side of the engine and then around and down the back with the start wire and connect it to the stud with the battery cable. No need to run it way back to the battery. Size of the wire would be determined by the output of your alternator. Step up to 8 gauge if your alternator is 80 amp or greater. 10 gauge is good otherwise. Safer than running it in and out thru the fire wall and along with other parts of the harness. Shorter run of this wire would also be better.

 

Routing it this way will shorten total length to roughly 6 ft. Sounds like a good idea. What about location of the inline 125 amp fuse. Should it be close to one end of the wire or anywhere that’s easy to access?

 

All that fuse will do is protect that one wire, IF there is a short.
I consider it unnecessary.
But if you want to use it, I suggest it should be near the alternator.

 

Isn't that big fuse intended to go in the main battery feed to the fuse panel. Usually located close to where it is connected to the battery terminal on the starter solenoid or starter relay depending on the engine.

 

no the Rebel kit came with a fusible link for main feed. Charge wire kit came from vintage auto garage with a fuse.

 

Ok, so now I have read all kinds of recommendations from posts here, on other online sources like American Autowire and Google searches on what folks do and why. I am so confused on what to do for my charge wire other than I need to upgrade from 10 ga to 6 or 8 ga for my 90 amp alternator. The charge wire measures about 40” from alternator to bat post on firewall mounted solenoid.

Some folks don’t use any wire protection, some use fusible link, some use a fuse, some use circuit breaker and some use multiple fuses.

 

Think about what is involved and what COULD happen.
12 volt battery on one end. It has a lot of amps stored in it hopefully at all times.
Alternator that when engaged will provide a lot of amps. It can fail WOT and overwhelm the wiring but this is very rare.
The wiring between the two. It is sized to handle normal and peak loads.
So long as the system works as designed and is sized and installed properly, there should be no problems.
If the wiring is somehow shorted to ground, the battery will discharge enough to melt the wiring and fire.
If the engine is running and the alt spinning during this, it will melt the wiring and fire.
Best bet is to prevent shorting. Route the wire safely and protected.
The safety features will only work if they are between the short and the component providing power.
With engine off, the battery holds power. So protection should be at the battery.
With system charging, both ends have power. So protection should be at both ends.
But now you have introduced 2 new components and 4 more connection failure points.

 

Us an external charge wire as you are planning.

Upgrade to 8 ga to suit your alternator output, and put the fuse on the battery end.

If you are worried about an internal failure of your alternator add a fusible link on that end.

Most important part is make your wire crimps properly, mechanical connections tight and secure, and harness runs routed and anchored to prevent damage.

 

Wire sizing math and charts are easily available here and elsewhere. To my mind, I want to run a circuit once and have peace of mind that even after years of use, I don't have to inspect for issues.
This doesn't mean I'd run double ought for every circuit. However, the cost and weight penalties of running an 8 gauge versus 10 gauge is insignificant provided both are on hand. Research max output, wire length and figure out what is recommended.
Here's one from NAPA for auto use. Many online are for stationary, home or other uses.
https://knowhow.napaonline.com/automotive-wiring-guide/
Right near the top, it has 0-5 feet and going over to 80-100 amps it says 4 gauge. This is probably overkill, since the charging system is only max output under extreme situations for short periods. The chart does not mention constant rating, but considering the number which is much higher than others, it probably is.
However, since you are only making one harness (no big cost issue) and want it to never be a concern and you are running it near hot exhaust (affects circuit and insulation) why not?
Roadkill shows 6 gauge
https://m.roadkillcustoms.com/alternator-wire-gauge-chart/
Speedway says under 5 feet, 6 gauge. Over 5 feet, 4 gauge.
https://www.speedwaymotors.com/the-...0107?msockid=03c14b7ae4cf6470288f5d30e56765e3

However, this site has a couple links down the page.
https://www.autorewire.com/
The chart shows 100 amps as a 12 gauge wire,
https://www.autorewire.com/image/amps-wire-gauge-size-chart_436020.jpg
That seems very small compared to other recommendations!
but the basic rod circuit shows a 10 gauge wire in the generator output circuit.
https://3.bp.blogspot.com/_-z9Chr5k...AAAG0/9HuW_Dh2EwM/s1600/BasicHotRodWiring.jpg
The GM alt link is dead, but many others mention a 10 gauge output wire.

So I understand the confusion. But it's your car, your choice. I'd go overkill.

 

thank you for all the links. Browsed them all. I am going with 6 ga wire and the 125a fuse.

 

Just wanted to say a BIG thanks to folks on this thread who guided me through my first wiring harness install..!! All wires are roughed in now and it was a huge success. Just need to loom em up.
The only issues I’ve found are:

1) Ron Francis headlight switch not working as stated in their paperwork. It’s a 4 way switch; off, park lights, low, high beam. When switch is pulled out in 3rd click, low beams should have power but both low and high have power. I called them and they sending me another one.

2) my dash mounted oil pressure gauge is not working. The one threaded into the block is working. Dash gauge is a vintage SW 6v gauge with an inline voltage reducer installed. I’ve not started engine to let it run, only turned it over with coil wire disconnected. With ignition switch on, I getting 8.66 volts to sender and 5.74v to gauge. Any ideas?

 

Please provide more info.
Like this?
www.ebay.com/itm/396361691969?msockid=135791a3119469b22d5887ec10c068d4
Car is 12 volts, with a big honkin' alt, right?
The inline voltage reducer is before gauge and/or sender, right? Should be 12v in, 6 v out. Depending on the meter used this may vary, depending on the reducer.

Which way does the sender work? Usually they are zero ohms at zero pressure, higher resistance at higher pressure. However, different manufacturers did things different. How many wires on sender and gauge?

 

Yes 12v system on pickup with 90 amp alternator. Inline reducer at gauge. Power to gauge is daisy chained from another 12v gauge not direct from fuse panel. Gauge has 3 terminals; ground, ign, sender. Sender is SW #279-A and I have 1 wire connected to it. I do remember calling SW to get proper sender for that gauge. Can’t find my notes on ohm specs.

 

Okay so, keyed 12v power to gauges, this gauge is supplied roughly 6 volts input

, along with a ground and a sending unit wire.

I don't know how you are getting more voltage at the sender.
Since the sender unit is a single wire variable resistor to ground, the gauge should see 6 volts, the wire from the gauge to the sender (disconnected) should be the same.




You can leave the sender disconnected and connect your meter to the sender connection not the wire and ground in OHMS. It will show the resistance at zero PSI.

Speedway says this sender has 240 ohms resistance and 80 psi.
SW says 240-33 ohms.
https://www.stewartwarner.com/products/sender-pressure-279a/
same here.
https://vehiclecontrols.com/shoppin...heavy-duty-thick-film-pressure-sender-80-psi/

Crank it over again (coil disconnected) and the sender resistance should change as pressure builds.
It may be zero PSI = 33 ohms, or zero PSI = 240 ohms. 80 PSI will be the other end of the range.

 

At 0 psi=229 ohms, at 40 psi=185 ohms

 

So long as that matches the gauge, you should be ready to go.

 

I have my radio under my rear seat and can't get it to turn on. I check the wiring and I'm getting 12v to the radio. I hooked the radio to the battery and it turns on. I'm wondering if the ground strap that i have to the firewall isn't enough or is to far away???

 

Its the radio itself properly grounded under the seat? If everything else electrical is working taillight etc I would think your ground to the body is fine.

 

I have the radio grounded to the sheet metal right next to it.... haven't got the lights or much else in yet.

 

If it works connected to battery + and -, either the power or ground isn't working in it's installed location.

 

Not sure if it date admit this here looked at the fuse diagram and it about slapped me in the face.... another fuse. Some how I popped the fuse swapped it out the radio comes on and the power antenna works

 

Looking at the wiring diagram for the gauges and saw there's an instrument power wire. Just curious is that what sends the power to the sending units, water, oil, gas, then the circuit is complete coming back to the gauge?

 

The "gauge power" wire supplies voltage to the gauges and then each "sender" wire runs to appropriate sender, which grounds thru the variable resistance determined by the oil pressure, fuel level, or temperature and the resulting current flow determines the reading on the gauge.

The gauge power wire in this picture is the pink wire daisy chained and powering each gauge.

 

Also, since it seems electric is your Achilles Heel, make sure this is only powered with ignition on, not battery (always on).
Wiring is sometimes confusing, can get messy, but just bite off a small chunk at a time.

To better understand how this circuit works, think about a house dimmer switch.
Power in, Variable Resistor (dimmer knob or sender) and visual indication (light brightness or gauge). There are a ton of differences involved, but that gives the basic idea.

 

im sure somewhere in this thread is the answer im looking for.... where is the best place to pick up power for the electric choke? I have a 9 t 3 harness

 

First, it will be a switched source, not full time. Second, you want a circuit rated and sized for the task. What is the amp rating of the choke and how long will the wiring be?

 

If you're using an 'old style' Ford or GM alternator with an exterior regulator, there will be a connection on the alternator you can use. These typically have four labeled bolted connection points on them: output to the battery, rotor/field (slip ring brush), ground, and field/stator. It's this last one you can use. This is the center point of the star-connected output windings. When the alternator is running, there's about 10 volts AC available at this point and enough current to operate the choke. This allows a short wire, and no need to run it back to the fuse panel or a switch as power isn't there unless the motor is running. As the choke heater is a resistive-only circuit, it doesn't care if its AC or DC. Sorry, you mopar guys are out of luck...

I don't believe the 'modern' alternators have this connection, but you could check. Sometimes the old ways are better...

 

I think the choke is less then 1 amp