New Alternator Wiring Upgrade Configuration

[svxcess]

Since I was putting in the new high-output alternator, I have come up with and completed a cleaner version of the alternator wiring mod, which actually removed some of the original wires that the wiring upgrade made unnecessary. So I fabricated the new wires ahead of time and they were installed by svxfiles and myself when we installed the new alternator.

First a little history:

ORIGINAL CONFIGURATION added three wires to the electrical system:

.....▪ 4 gauge power wire from the alternator charging post to the positive terminal of the battery.
.....▪ 4 gauge wire from the negative battery terminal to frame ground.
.....▪ 4 gauge wire from the negative battery terminal to engine ground.


The older original stock wires become corroded and brittle with age at the connectors and the wires themselves, causing resistance and diminished current flow; the same with the ground connections.

With the larger added wiring, there was ample current flow from the alternator to the battery. (The alternator case is its own ground) The engine was now solidly grounded to the battery and the battery was solidly grounded to the chassis. There was about a 2 volt increase that was noticed.

THE IDEA
With alternator current now flowing freely and following the path of least resistance through the new larger wires, the original wires were not being used and seemed redundant. Unnecessary wires that were deteriorating and faulty connectors seemed to be no longer of any use, so why keep them?


Looking inside the original black plastic wiring channel that runs along the rear of the A/C compressor and alternator you will find two white wires that attach to the alternator charging post. One of these goes back to the battery through a fusible link and the other goes to one side of the ignition switch. Using a multimeter, I found that the two white wires have approximately the same voltage at the alternator connection as is measured at the battery.

The two wires from the alternator plug also are housed inside this plastic channel and three wires on top of the A/C compressor enter this channel further down.


NEW CONFIGURATION

Battery negative terminal:
The larger ground wires from the negative battery terminal to frame ground and engine ground are still being used, but the smaller, original ground wire is now useless and was removed. I used a different type of connector for these wires to increase conductivity with a stronger connection.

The plastic wiring channel was opened, the wires removed from inside and the plastic channel was discarded.


Alternator connection:
I removed the two white wires and cut them back about two feet. One of these wires was factory-spliced into three wires close to the battery. I put new ring connectors on each of these wires and connected them directly to the positive post of thebattery. They are still in the circuit and have the same voltage flowing through them, only now they are connected at the battery and not at the alternator.

The alternator plug wires were lengthened, soldered and shrink-wrapped and encased in heat-resistant nylon/ fiberglass braided sleeving and routed behind the alternator and under the intake manifold and reconnected at their original position by the battery. The same thing was done to the two small A/C connectors. These are protected and hidden out of sight for a clean, uncluttered look.

So all that remains is one single 4-gauge power wire, which runs across the top of the engine from the alternator charging lug to the positive battery post, through a 175A inline megafuse for protection. This single wire replaces both of the original white wires originally at the alternator; one of which the original charging wire with the fusible link protection. The fusible link was not removed.

OVERVIEW OF WIRING

All 4 gauge is by “Streetwires” and is high-density, fine strand, 100% oxygen-free copper that has been tinned to prevent corrosion.

All connectors have been crimped, soldered, and sealed with heat-shrink tubing.

All wire splices have been either soldered and shrink-wrapped or use butt connectors which were crimped and covered with shrink wrap.

Connections use a thin dielectric grease coating for corrosion protection.

I am also keeping a log on voltages and performance. On my trip home last night I noticed that, as the brushes in the alternator became broken in and began to seat properly, my voltage increased. By Reading X I should be able to give a full report.

.

[Mike621]

John,

I'm looking forward to your results. I need to redo the wiring for two of my SVXs.

[benebob]

You're now officially in the modified class for judging purposes. Why did you want a higher output anyways? I'd be very leary about sending more juice through wires that weren't designed to support it. A melted wiring harness or a burning Polo isn't a pretty thing to see!

[Mike621]

Originally Posted by benebob

You're now officially in the modified class for judging purposes. Why did you want a higher output anyways? I'd be very leary about sending more juice through wires that weren't designed to support it. A melted wiring harness or a burning Polo isn't a pretty thing to see!

Uh oh! The next thing you know he'll want a 5spd and coilovers!

[svxcess]

Originally Posted by benebob

You're now officially in the modified class for judging purposes. Why did you want a higher output anyways? I'd be very leary about sending more juice through wires that weren't designed to support it. A melted wiring harness or a burning Polo isn't a pretty thing to see!

The high output alternator does not put out excessive current unless there is a demand for it. For example, at idle, a vehicle's electrical loads may exceed the low-speed current (amperage) output of the alternator and when this happens the shortfall comes from the battery. This will result in a drop in the electrical system voltage as the battery delivers the additional electrical current to meet the demand. This is equivalent to the brown-outs experienced by homes and businesses when the electrical demand is more than the supply. This is where the benefits of high-output alternators come in.

A higher-amp output alternator will not harm your battery or charging system in any way, as long as you add a larger 4 gauge charging wire between the alternator and the battery.

A good rule of thumb is that more amps are not harmful, but more voltage is. If you look at electrical power like water, amperage is equivalent to the volume of water, and voltage is equivalent to water pressure. More amperage is like having a larger pool of water to draw from when you need it.

During the winter, the loads placed on our electrical system are greatest. Winter driving, and the need to use current-hungry applications, such as heating/defrosting, rear window and mirror defrosters, lights, etc. are with us almost always in multiple combinations. Since high-output alternators are capable of putting out about half of their rated output at idle, this is where the benefit comes in.

You could use the same current-hungry applications with the stock alternator and it would struggle to supply the same current demands at idle. since it was not designed for low-speed output.

The original, older, corroded wires that I removed would be more of a hazard if left in. High resistance to current flow creates excessive heat and wiring breakdown is more likely.

If you haven't already, read my "Alternator 101" in THIS POST for more information.

This mod was not a frivolous impulse. I researched this for a long time, spoke with electronic engineers and electrical engineers with expertise in automotive electrical systems. They all agreed that this was a totally safe and reliable mod, with no adverse consequences. I had even sent them the Power Supply Routing schematics from the SVX wiring manual.

,

[Trevor]

When the modification referred to was first proposed, I was contacted by e-mail for advice. I set out the necessary requirements in detail, not knowing the reason for replacing all wiring, which it now turns out was corroded.

It would appear that several connections have been made directly to the battery, which means these sub circuits now have no protection against short circuit. This original wiring was routed via the fuse box and connected to a bus bar type positive point, so as to be protected by the fusible link.

If others regarded this apparent modification to be a satisfactory arrangement, I disagree. Subaru knew what is required and a live wire insurance assessor could well use the mod. to disclaim any insurance.

[sicksubie]

Trevor is back!!!

[Tim]

Originally Posted by svxcess

ORIGINAL CONFIGURATION added three wires to the electrical system:

.....▪ 4 gauge power wire from the alternator charging post to the positive terminal of the battery.
.....▪ 4 gauge wire from the negative battery terminal to frame ground.
.....▪ 4 gauge wire from the negative battery terminal to engine ground.

This is a common method used by car audio enthusiasts to minimize voltage drops. This is often referred to as the big three. I originally was planning on tackling this project, but have pushed further down on my to-do list.

Pretty clean setup as always John. Can't wait to hear your results at Reading

[Mike621]

Originally Posted by Trevor

When the modification referred to was first proposed, I was contacted by e-mail for advice. I set out the necessary requirements in detail, not knowing the reason for replacing all wiring, which it now turns out was corroded.

It would appear that several connections have been made directly to the battery, which means these sub circuits now have no protection against short circuit. This original wiring was routed via the fuse box and connected to a bus bar type positive point, so as to be protected by the fusible link.

If others regarded this apparent modification to be a satisfactory arrangement, I disagree. Subaru knew what is required and a live wire insurance assessor could well use the mod. to disclaim any insurance.

The reason I am seeking guidance with replacement of these wires is mainly because of corrosion. I suppose I'll go for something closer to factory spec, if possible.

[SVXRide]

I believe the key discussion point here is protecting the battery via fusible links or 100A fuses (i.e., the need to add them, given the new wiring)
-Bill

[benebob]

Originally Posted by svxcess

A higher-amp output alternator will not harm your battery or charging system in any way.

A good rule of thumb is that more amps are not harmful, but more voltage is. If you look at electrical power like water, amperage is equivalent to the volume of water, and voltage is equivalent to water pressure. More amperage is like having a larger pool of water to draw from when you need it.

,

Unfortunately this statement is compeltely wrong. A higher amp output alternator CAN harm your wiring harness drastically if not done properly. Any component downwind of all the properly gauged fuses will be fine as the fuses prevent more amps from flowing there BUT any wiring prior to a properly gauged fuse or fusable link (which is based on the wire size needed to transmit the amps flowing through the wire) is subject to overheating and failure if not changed to deal with the added amps from the new alternator.

If you don't believe me, why don't you change a 15 amp fuse to a 30 amp fuse and run a 30 amp component through those wires meant for a 15 amp component. I'll provide the Hershey bars, crackers and marshmellows you'll be providing the eventual fire. Would you like almonds or plain chocolate?

I'm fairly certain you are very much aware of this John as you're as anal as the best of us when it comes to your decisions. I'm also fairly sure that your circuits WILL be protected with a fusable link allowing only the factory specified amps to flow through any not upgraded in size wiring, however, not everyone is as anal nor willing to examine all aspects of the electrical system when changing it. A simple read of your plan doesn't specify exactly where and what is being changed. To do only part of what you're doing can and eventually will lead to an major issue once there is more draw then the wires can handle. Of course this is most likely to occur in cases of accidents or unprotected components grounding, not in your average day but a horrible day none the less.

[svxcess]

Maybe I have been unclear.

I have not removed any of the fusible links from the system. All I have done is shortened the wires by about 2 feet, which were originally connected at the alternator post, and connected them straight to the battery.

With the normal wiring upgrade in place, measuring the normal voltage at the alternator post, where these wires were attached, was the same as at the battery terminal. It is getting the same current and voltage, just at a different junction. The original circuitry and fusible link protection has not been touched or removed-- just two pieces of old wire. We added new ring terminals to the original (same gauge) wire and connected them

I do not have mega-gazillion watt stereo amplifiers that need the extra current draw. I will be drawing the same current from this alternator as the stock one it replaced, to fulfill the requirements of our stock electrical system at any given time. I still have the 60A inline fuse in the main wire from the alternator to the battery as additional protection.

It just gives me the same amperages that I need, but at a lower RPM. At idle, with my turn signals operating, I do not hear the change in fan speed of my climate control like I used to.

If my car hasn't burned to a crisp by then, take a closer look at this at Reading. Even svxfiles had absolutely no concerns with this arrangement-- maybe he can shed some additional insights on this.

.

[Francis]

waiting for pics

[SVXRide]

Originally Posted by svxcess

Maybe I have been unclear.

I have not removed any of the fusible links from the system. All I have done is shortened the wires by about 2 feet, which were originally connected at the alternator post, and connected them straight to the battery.

With the normal wiring upgrade in place, measuring the normal voltage at the alternator post, where these wires were attached, was the same as at the battery terminal. It is getting the same current and voltage, just at a different junction. The original circuitry and fusible link protection has not been touched or removed-- just two pieces of old wire. We added new ring terminals to the original (same gauge) wire and connected them

I do not have mega-gazillion watt stereo amplifiers that need the extra current draw. I will be drawing the same current from this alternator as the stock one it replaced, to fulfill the requirements of our stock electrical system at any given time. I still have the 60A inline fuse in the main wire from the alternator to the battery as additional protection.

It just gives me the same amperages that I need, but at a lower RPM. At idle, with my turn signals operating, I do not hear the change in fan speed of my climate control like I used to.

If my car hasn't burned to a crisp by then, take a closer look at this at Reading. Even svxfiles had absolutely no concerns with this arrangement-- maybe he can shed some additional insights on this.

.

John,
Go back to Ben's comment regarding "upstream of fuses". My concerned would be the the shortened wires heating up/burning prior to the fuseable link going, as you can now - potentially - get more amps flowing through them with the upgraded alternator. Just something to consider.
-Bill

[benebob]

No John, you've been perfectly clear to me but unless the wire is heavier than it should be you SHOULD be replacing it with a larger gauge (actually a smaller number wire) since you'll have more amps running through it to the battery, I would suspect that the Subaru didn't use a heavier gauge wire there as it is a weak point of the car once it starts to degrade and what the starter is on that direct circuit too I think. Look at it this way. In your house you have 12 gauge wire and 14 gauge wire. 14 gauge is good for only 15 amps, 12 gauge is good for 20 amps. Yes that is ac not dc but the principles are the same. You will be heating up that wire faster under normal conditions, you will be degrading it faster and eventually if left in use long enough it can fail or worse start a fire.

I'm no sparky nor do I want to be but any how to electrical book will tell ya which wire to use based on the number of amps going through it.

You could simply remain stock and keep your contacts and wires clean and in good shape. Why don't you remove the plastic from your harness and start polishing!

Originally Posted by svxcess

Maybe I have been unclear.

I have not removed any of the fusible links from the system. All I have done is shortened the wires by about 2 feet, which were originally connected at the alternator post, and connected them straight to the battery.

With the normal wiring upgrade in place, measuring the normal voltage at the alternator post, where these wires were attached, was the same as at the battery terminal. It is getting the same current and voltage, just at a different junction. The original circuitry and fusible link protection has not been touched or removed-- just two pieces of old wire. We added new ring terminals to the original (same gauge) wire and connected them

I do not have mega-gazillion watt stereo amplifiers that need the extra current draw. I will be drawing the same current from this alternator as the stock one it replaced, to fulfill the requirements of our stock electrical system at any given time. I still have the 60A inline fuse in the main wire from the alternator to the battery as additional protection.

It just gives me the same amperages that I need, but at a lower RPM. At idle, with my turn signals operating, I do not hear the change in fan speed of my climate control like I used to.

If my car hasn't burned to a crisp by then, take a closer look at this at Reading. Even svxfiles had absolutely no concerns with this arrangement-- maybe he can shed some additional insights on this.

.