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Old 10-12-2019, 03:32 PM
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Electrical Gurus please chime in

Is there any downside to running a positive lead to the alternator from a junction block where the + 10 awg wire from the battery is connected? I’m completely wiring my hot-rod from scratch, and I’m planning on using this same block for several positive feeds. Appreciate the help/advice.

Ed

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Old 10-12-2019, 06:10 PM
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Electrically it's fine. The only thing to watch out for is that it is potentially one more connection that can eventually corrode and cause a problem. Use dielectric grease to protect the terminals.
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Old 10-12-2019, 06:42 PM
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This is roughly how I wire mine;




I have never had a problem using a positive post which also doubles as a isolated through firewall connection.

By running it in this manner the starter is allowed to have full voltage first and you can run a lesser amp cutoff/Kill switch (or key if you do not want a cutoff) to supply voltage to the rest. Your alternator will charge your Post first reducing voltage drops then your battery.

This allows you to run a neat loom of wiring along the top of the intake near the head. The I/Indicator was shown as is for simplicity that also runs along top the intake.


Negative wiring not shown for simplicity.

I run the negative N/NEG/- off the alternator to the intake. At the back of the intake I have a 4(or larger) gauge wire going to a Negative firewall post which grounds the engine. The battery negative runs along the frame rail and up along the side of the firewall to this post.

The Negative post grounds the Engine, frame, firewall/body. As well a 4 gauge wire going to the back of the car to a junction point for the rear relays supplying the fuel pump, taillights, etc. This eliminates the frame as a ground lessening grounding issues from corrosion allowing for once again easy maintenance and simplicity.

Using a negative post keeps things neat, away from heat and allows for easy maintenance. No wiring looming off the front of the engine going to the battery or using the frame as a ground having connections exposed to the elements.


I like easy maintenance and will pull a engine to do like a oil pan. By wiring in this manner I am allowed to pull the battery post, pull the starter leaving the wiring attached to the starter, remove the bolts from the positive and negative firewall through post, pull the exhaust flanges, fuel lines, cap/rotor, carb (or plastic intake) installing the motor plate, engine mounts, and transmission bolts if not pulling the transmission with engine.
No hard to reach bolts or messing around with that one wire you forgot about.
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Old 10-13-2019, 05:58 AM
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If you check the junkyards you will find that the GMT400 trucks (88-98) used a junction block and wiring similar to your plan. The 8 or 10 gauge power lead from the starter goes up to a junction strip on the firewall, and then the alternator charge and other wiring connects there. The OEM power junction is a nice heavy duty part with about 5-6 threaded posts. Most of the junctions you pull will have several wires attached that have fusible links, so you get overcurrent protection along with the junction.

Bruce
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Old 10-13-2019, 06:52 AM
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Great stuff, thanks for the input guys!

Ed
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Old 10-14-2019, 05:23 AM
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This is how mines wired
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Old 10-14-2019, 10:33 AM
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Hey there EOD guy
Appreciate the input, I wish I could read the text better on your attachment. Not sure if you’re showing the battery in your diagram

Ed
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Old 10-16-2019, 12:51 AM
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My S15 mounts the battery back in the bed. The B+ main power cable runs the length of the truck to a marine terminal mounted where the battery used to be with a 90 amp fuse close to the terminal. That is power central; the starter cable originates from there back to the starter, all housekeeping B+ originates there and goes to the original fuse box and a couple remote fuse boxes in the cab, and the alternator output anchors on that terminal. I built this thing about 25 years ago and nary a problem in all that time. And where I live we get a lot of rain, a little snow and mighty few sunny dry days so corrosion should be an issue but hasn't been.



But I do protect my connections with dielectric grease, RTV, and shrink tubing or shrink tape. My crimps on heavy wire and cables are made with a hydraulic crimper, wonderful tool on heavy gauge wires. One of my tricks is to insert the cable into the lug with a generous supply of dielectric grease. Then do the crimp and wipe off the squished out grease then smear a coating of RTV over where the shrink sleeve will locate, then bring it up the cable to position and put the heat gun on it. Once the shrink is done wipe off the squeezed out RTV and put it to work. Where I have gauge changes or different gauge taps I use intermediate sizes of shrink tube to fill the needed largest shrink tube, then shrink it all together, this is as good as a molded in connection for keeping the weather out.



Bogie
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Old 10-16-2019, 06:15 AM
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Thanks for the input. The fact that you’re not having any corrosion issues, is a testament to your workmanship! Cool 😎
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Old 10-19-2019, 08:16 AM
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Quote:
Originally Posted by Eddie Salinas View Post
Is there any downside to running a positive lead to the alternator from a junction block where the + 10 awg wire from the battery is connected? Iím completely wiring my hot-rod from scratch, and Iím planning on using this same block for several positive feeds. Appreciate the help/advice.

Ed
No downside at all. But if you're starting from scratch, might as well use 8 gauge wires for the the charging circuit, especially if alternator is rated at 100 amps or more or you have electric radiator fans. Heck, the generic American Autowire kit I used in my 82 Chevy pickup came with 6 gauge wires (!) for the charging circuit. Actually overkill for my base truck with 60-something amp alternator. Since those big wires are a pain to route, I ended up using 8 gauge wires for charging circuit and fuse panel/ignition switch feed.

Also, if it's a 2-wire alternator, run the "sense" wire to that same point on the distribution block. That way the regulator will try to maintain 14.2 volts at the block. Back in the day, GM ran everything together at a soldered "splice". Kind of crude but it worked.

You might also want to consider using a fuse between the distribution block and the BAT stud on the starter to protect the battery.

Finally, be sure to use high temperature "cross-linked" GXL and SXL wire, not the stuff you buy at auto parts and hardware store. I found that Jeg's has the best prices by far for 25-ft rolls.

Here's a pic of the 6 gauge charging circuit kit and 150 amp fuses that came with my AAW harness. I used 8 gauge and a single 100 amp fuse.
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Old 10-19-2019, 08:22 AM
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I'm confused about using dialectic grease, which is a NON-CONDUCTOR of electricity. Guess I need to do some research here.

I typically use external star washers under ring terminals to "bite" into terminal and terminal block. Also for ground wires.
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Old 10-19-2019, 02:07 PM
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Quote:
Originally Posted by 55_327 View Post
I'm confused about using dialectic grease, which is a NON-CONDUCTOR of electricity. Guess I need to do some research here.

I typically use external star washers under ring terminals to "bite" into terminal and terminal block. Also for ground wires.

Any tight connection will squish out enough dielectric grease to make a good connection, although using conductive grease I suppose would be better IF it also protects against corrosion. Same thing goes for things like temp sending units if you use sealant or teflon tape. It cuts right through to get a good ground. Same for head bolts with sealant on them. The sealant only stays in the spaces in between the threads.
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Old 10-19-2019, 02:09 PM
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Quote:
Originally Posted by 55_327 View Post
I'm confused about using dialectic grease, which is a NON-CONDUCTOR of electricity. Guess I need to do some research here.

I typically use external star washers under ring terminals to "bite" into terminal and terminal block. Also for ground wires.
I agree, dialectic grease is non-conductive, and also not recommended on rubber products. Silicone grease is better for rubber, but the guy said he hasn’t had any issues for a very long time, so I wonder about the validity of the rubber concern. I’m planning on clean/dry surfaces, tighten everything down good, use star washers like you mentioned, then apply some grease to conductive surfaces to help keep moisture etc from being an issue. I’m also using shrink sleeving and plastic looms when I’m done...


Ed
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Old 10-19-2019, 02:14 PM
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Quote:
Originally Posted by Eddie Salinas View Post
Is there any downside to running a positive lead to the alternator from a junction block where the + 10 awg wire from the battery is connected? Iím completely wiring my hot-rod from scratch, and Iím planning on using this same block for several positive feeds. Appreciate the help/advice.

Ed

It's just fine. I suggest a fuse inline between the junction and the alternator and between the junction and the battery. I have a 70 or 80 amp fuse in both locations even though the alternator is something like 93 amp. I never needs to put out that much current, I just figured an over rated alt. won't run as hot as one rated for less current and hopefully last longer.
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Old 10-19-2019, 02:43 PM
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Copper and oxygen dont mix. Dielectric grease is used as a "filler" to fill in those gaps between the strands of wire.

Then you cap it off and shrink that cap for a air tight seal. You clean both surfaces with a copper brush, bolt the two pieces of copper toghter then I have a can of flat black paint the same as the firewall that I shoot over the bolt.

This all being done. When I build a system I add a extra foot in the 4+ gauge wires which allows me to cut back and recrimp the ends with new terminals every 2 to 5 years(when I replace the battery) depending on the conditions the electrical system has seen.
The 16 to 8 stuff I just replace with new. But with 4 to 0000 wire you try and make that last.

2 years is a extreme. Something that is sumbreged in mud, ice, water which is always mixed with stuff, heat, vibration, shockloads, and the occasional roll twisting the body/frame.

If your just running on the street 5 to 6 years is a good mark to cut back your connections. If you live in a dry climate you could push it back further.

Before you do something like a cross country drive or something like power tour giving your electrical system a check up pays off. You do not want something like a breakdown at 2AM in West Texas or find yourself out in Mojave with a charging problem.



Most of our rides came factory with through firewall blade connections that are very prone to condensation. This makes them very unreliable eventually causing all kinds of shorts. Now you can seperate the pieces every 5 to 6 years and brush down the blades which will help discover bad connections, burnt/rippled wiring, and broken blades before adding dielectric grease to refresh this and extend its life.
After 10 to 20 years depending on the conditions you can get that green goop where separating the 2 halfs usually destroys it with several connections fused while others are loose.

The best system is to move those vulnerable blade parts inside the cab where the encounter with water and condensation from a faulty firewall weather striping is lessened.
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