ALT/Battery wiring questions

[jjvh5150]

Changing my alt/battery wiring and would like to know if how I want to do it will work.
Current wiring is- battery to starter, 1 and 2 are stock, 8ga. wire from batt post on alternator to starter.
What I would like to do is- Battery to starter, keep 1 and 2 stock, replace 8ga. with 4 ga. wire from the batt post and run to junction block instead of starter and another 4 ga. wire to battery from the batt post on the alternator.
Would this work?

 

[CalSgt]

I don't quite understand exactly what you are wanting to do, or what "1 and 2" are but...

I recommend leaving the stock starter battery positive wire and stock block ground in place, those are typically really heavy gauge quality stuff and the reliability of your vehicle depends on them. By changing how they work you can induce an unforeseen failure point that could leave you stranded

If you want to upgrade your charging system you do not really need to change the starter wire. Just upgrade the charge wire to the battery and add the same gauge wire to ground. Research "Big 3" or "Big 5" wiring upgrades there's all kinds of write ups on it, most of them recommend only adding to existing alternator charge and ground wiring and to leave the stock stuff in place.

Mine is kinda custom and I went way overboard due to the amount of electronics and stereo equipment I installed:
Stock starter Batt + wire
Stock Batt - ground to block

Power
0 Ga from Batt + to fused junction block
4 Ga from Alt to fuse block
4 Ga from fuse block to truck wiring bulkhead
4 Ga from fuse block to stereo amp
8 Ga from fuse block to electric fan controller

Grounding
0 Ga from Batt - to frame
4 Ga from frame to engine block
4 Ga from alt case to frame
4 Ga from Cab to Frame
4 Ga from Amp to Cab (same mounting point as Cab to Frame ground)

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[jjvh5150]

I don't quite understand exactly what you are wanting to do, or what "1 and 2" are but...

I recommend leaving the stock starter battery positive wire and stock block ground in place, those are typically really heavy gauge quality stuff and the reliability of your vehicle depends on them. By changing how they work you can induce an unforeseen failure point that could leave you stranded

If you want to upgrade your charging system you do not really need to change the starter wire. Just upgrade the charge wire to the battery and add the same gauge wire to ground. Research "Big 3" or "Big 5" wiring upgrades there's all kinds of write ups on it, most of them recommend only adding to existing alternator charge and ground wiring and to leave the stock stuff in place.

Mine is kinda custom and I went way overboard due to the amount of electronics and stereo equipment I installed:
Stock starter Batt + wire
Stock Batt - ground to block

Power
0 Ga from Batt + to fused junction block
4 Ga from Alt to fuse block
4 Ga from fuse block to truck wiring bulkhead
4 Ga from fuse block to stereo amp
8 Ga from fuse block to electric fan controller

Grounding
0 Ga from Batt - to frame
4 Ga from frame to engine block
4 Ga from alt case to frame
4 Ga from Cab to Frame
4 Ga from Amp to Cab (same mounting point as Cab to Frame ground)

You must be registered for see images attach

1 and 2 are the 2 wire plug on back of alternator. Keeping the starter cable. Adding a power wire from the alt to the battery and to the junction box on the firewall is what I want to do.

 

[Bextreme04]

1 and 2 are the 2 wire plug on back of alternator. Keeping the starter cable. Adding a power wire from the alt to the battery and to the junction box on the firewall is what I want to do.

From the factory, you should not have a power wire running from the alternator to the starter. There should be a charge wire from the alternator to the junction box on the firewall. If you don't have an upgraded alternator, there is no reason to change anything. If you upgrade to a 90amp or higher alternator, I would suggest getting an 8 gauge charge wire from a GMT-400 and run it from the alternator charge post straight to the battery. Make sure you have a large ground(4awg or larger) from the alternator bracket to the frame and from the frame to the negative terminal on the battery.

 

[CalSgt]

1 and 2 are the 2 wire plug on back of alternator. Keeping the starter cable. Adding a power wire from the alt to the battery and to the junction box on the firewall is what I want to do.

From the factory, you should not have a power wire running from the alternator to the starter. There should be a charge wire from the alternator to the junction box on the firewall. If you don't have an upgraded alternator, there is no reason to change anything. If you upgrade to a 90amp or higher alternator, I would suggest getting an 8 gauge charge wire from a GMT-400 and run it from the alternator charge post straight to the battery. Make sure you have a large ground(4awg or larger) from the alternator bracket to the frame and from the frame to the negative terminal on the battery.

@Bextreme04 is right, unless you are upgrading the charging system there shouldn't be much need... IIRC though my alternator charge wire had a "Y" in it and went to both the junction and the positive lug of the starter. I could be mistaking it for the second wire that went from my starter positive lug though, its been a while since I rewired my truck.

If you replace this stock wiring be aware both wires from the starter positive lug AND the wires leaving the junction on the firewall all have fusible links on them. If you replace those wires you need to figure a way to keep them protected by adding a fuse/fusible link/circuit breaker Etc. Otherwise, if you end up with a direct short you will burn the truck down.

Question:

Are you trying to repair a problem?
or
Are you trying to modify for performance/appearance?

 

[jjvh5150]

From the factory, you should not have a power wire running from the alternator to the starter. There should be a charge wire from the alternator to the junction box on the firewall. If you don't have an upgraded alternator, there is no reason to change anything. If you upgrade to a 90amp or higher alternator, I would suggest getting an 8 gauge charge wire from a GMT-400 and run it from the alternator charge post straight to the battery. Make sure you have a large ground(4awg or larger) from the alternator bracket to the frame and from the frame to the negative terminal on the battery.

I have a 105 amp alternator. PO ran a 8ga. wire from the alt output to the starter and was thinking of moving it from the starter to the junction block instead. I do have the stock wiring from the 2 wires and plan on keeping those. I also plan on running a 4ga. from the alt to the battery.

 

[jjvh5150]

@Bextreme04 is right, unless you are upgrading the charging system there shouldn't be much need... IIRC though my alternator charge wire had a "Y" in it and went to both the junction and the positive lug of the starter. I could be mistaking it for the second wire that went from my starter positive lug though, its been a while since I rewired my truck.

If you replace this stock wiring be aware both wires from the starter positive lug AND the wires leaving the junction on the firewall all have fusible links on them. If you replace those wires you need to figure a way to keep them protected by adding a fuse/fusible link/circuit breaker Etc. Otherwise, if you end up with a direct short you will burn the truck down.

Question:

Are you trying to repair a problem?
or
Are you trying to modify for performance/appearance?

Yes I also have the charge wire that y's and that is the wires I have labeled 1 and 2 and plan on keeping them. I am upgrading for performance and more power to cab if possible.All new power wires will be fused. Just want to know if it can be wired from the alt output to that junction box without causing problems.

 

[Ricko1966]

Changing my alt/battery wiring and would like to know if how I want to do it will work.
Current wiring is- battery to starter, 1 and 2 are stock, 8ga. wire from batt post on alternator to starter.
What I would like to do is- Battery to starter, keep 1 and 2 stock, replace 8ga. with 4 ga. wire from the batt post and run to junction block instead of starter and another 4 ga. wire to battery from the batt post on the alternator.
Would this work?

Just run a second 8 gauge to the battery positive

 

[CalSgt]

Yes I also have the charge wire that y's and that is the wires I have labeled 1 and 2 and plan on keeping them. I am upgrading for performance and more power to cab if possible.All new power wires will be fused. Just want to know if it can be wired from the alt output to that junction box without causing problems.

Yeah, I don’t see why not.

Upgrade your ground wires while you’re at it.

 

[jjvh5150]

Yeah, I don’t see why not.

Upgrade your ground wires while you’re at it.

Absolutely.First thing I did.

 

[Ricko1966]

Yes I also have the charge wire that y's and that is the wires I have labeled 1 and 2 and plan on keeping them. I am upgrading for performance and more power to cab if possible.All new power wires will be fused. Just want to know if it can be wired from the alt output to that junction box without causing problems.

Your new power wires need fusible links not fuses. Your cab power comes from the battery and battery cable. Adding a second 8 gauge wire to your existing setup will double the amperage capacity to charge the battery. I doubt the backside of the charging post( inside the alternator) has enough gauge to even support 2x8 gauge charging at full tilt. To be technical,find out max charge your alternator can produce, then see what gauge of wire or 2 wires are needed to support that,more than that makes your alternator a weak link. I would run 80 percent of what would be needed in a worst/best case scenario,use my wires as a limiter to keep from overheating my alternator. Also if you run a second lead,you now have a redundant circuit. 1 wire fails,the second gets you home.

 

[Dejure]

Detroit wiring is not about ideal for anyone but Detroit. Were it otherwise, our rigs would come with battery cut-outs, momentary switches to test lights to monitor phantom drains, wires for extra crap we don't have would not be included in ours, wires might replace relays. . . .

Inasmuch as whoever owned my truck before me shouldn't have, that is, was electrically challenged, I'm having to correct a lot of things.

One problem I ran into was, the battery would drain after a few days of sitting. Tracking down such things, especially if added circuits weren't fused, can be fun.

[SIDE NOTE: Turned out whoever wired the choke had it on 24/7]

Tired of removing the negative battery cable, I ran it to a large amp capacity cut out switch.

I may add the aforementioned momentary switch and light on a wire feeding back to the battery ground to the switch mounting bracket I made for it, so I can determine if something is drawing current (if you flip the switch and the light comes on, something is completing a circuit (e.g., parking lights, under-hood light. . . .)

I'll leave the bazillion amp power cable for the starter and the power feed to the starter solenoid, but, instead of using the starter as a junction, I'll install a junction on the firewall, where it can be gotten to with relative ease.

I might even feel compelled to install a ground terminal on the firewall, rather than adding more potential, future trouble spots (bad ground connections all over the truck).

The firewall junctions would be handy for things like, a stereo install, electric seats, additional gauges (e.g., Tire Pressure Monitor, Fuel-Air Ratio Monitor, etc.), fog lights, and, of course, additional circuit fuses.