Fox Battery Relocation

[Knowbody]

Will this schematic work for battery relocation?

'91 LX Coupe 5.0
Optima Red Top relocated to trunk in NHRA Approved box
3G Alternator
Jegs 2-Post Disconnect Switch
OEM Starter Solenoid relocated to trunk near battery
Painless Performance Power Distribution Block
1/0 gauge cables

 

[CarMichael Angelo]

Looks fine to me. The only addition is to run the main GND directly from the bat to the engine block.

 

[jrichker]

For a battery cut off switch, see http://www.moroso.com/catalog/categorydisplay.asp?catcode=42225
is the switch http://www.moroso.com/catalog/images/74102_inst.pdf is the installation instructions.
Use the super duty switch and the following tech note to wire it and you will be good to go.

Use the Moroso plan for the alternator wiring and you risk a fire. The 10 gauge wire they recommend is even less adequate that the stock Mustang wiring.

There is a solution, but it will require about 40' of 18 gauge green wire.

Wire the battery to the two 1/2" posts as shown in the diagram.

The alternator requires a different approach. On the small alternator plug there is a green wire. It is the sense lead that turns the regulator on when the ignition switch is in the run position. Cut the green wire and solder the 40' of green wire between the two pieces. Use some heat shrink to cover the splices. See http://fordfuelinjection.com/?p=7 for some excellent help on soldering & using heat shrink tubing.

Run the green wire back to the Moroso switch and cut off the excess wire. Try to run the green wire inside the car and protect it from getting cut or chaffed. Crimp a 18 gauge ring terminal (red is 18 gauge color code for the crimp on terminals) on each wire. Bolt one ring terminal to each of the 3/16" studs. Do not add the jumper between the 1/2" stud and the 3/16" stud as shown it the
Moroso diagram.

How it works:
The green wire is the ignition on sense feed to the regulator. It supplies a turn on signal to the regulator when the ignition switch is in the Run position. Turn the Moroso switch to off, and the sense voltage goes away, the voltage regulator shuts off and the alternator quits making power.

The fuse & wiring in the following diagram are for a 3G alternator. The stock alternator uses a dark green fuse link wire that connects to 2 black/orange wires. Always leave them connected to the starter solenoid even if you have a 3G alternator.

Rear mounted battery ground wiring. Follow this plan and you will have zero
ground problems.

One 1 gauge or 1/0 gauge wire from battery negative post to a clean shiny spot on the chassis near the battery. Use a 5/16” bolt and bolt it down to make the rear ground. Use a 1 gauge or 1/0 gauge wire from the rear ground bolt to a clean shiny spot on the block.

One 4 gauge wire from the block where you connected the battery ground wire to the chassis ground where the battery was mounted up front. Use a 5/16” bolt and bolt down the 4 gauge engine to chassis ground, make sure that it the metal around the bolt is clean & shiny. This is the alternator power ground.

The computer has a dedicated power ground wire with a cylindrical quick connect (about 2 ½”long by 1” diameter. It comes out of the wiring harness near the ignition coil & starter solenoid (or relay). Be sure to bolt it to the chassis ground in the same place as you bolted the alternator power ground. This is an
absolute don’t overlook it item for EFI cars
Note: The quick disconnect may have fallen victim to damage or removal by a previous owner. However, it is still of utmost importance that the black/green wires have a high quality ground..

Picture courtesy timewarped1972

Crimp or even better, solder the lugs on the all the wire. The local auto stereo shop will have them if the auto parts store doesn't. Use some heat shrink tubing to cover the lugs and make things look nice.



See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring
http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

 

[Chuckman]

For a battery cut off switch, see http://www.moroso.com/catalog/categorydisplay.asp?catcode=42225
is the switch http://www.moroso.com/catalog/images/74102_inst.pdf is the installation instructions.

Those links there are dead, but iirc this is the switch on summit: https://www.summitracing.com/parts/mor-74102

Note that for it to be NHRA legal, it has to shutoff both the positive wire AND the regulator as shown

 

[jrichker]

Those links there are dead, but iirc this is the switch on summit: https://www.summitracing.com/parts/mor-74102

Note that for it to be NHRA legal, it has to shutoff both the positive wire AND the regulator as shown

I don't know about the NHRA, but I do know about Ford. Alternators, unlike generators of old, have no residual magnetic field. Therefore when you shut off the field power, the alternator shuts down.

When you disconnect the green/red wire from the alternator, you shut off the regulator power feed to the field windings which turns the alternator off just like you turned the ignition switch off

 

[Knowbody]

My car has the 3G alternator installed, running for over a year with no issues, with the main power being fed off the solenoid in the stock fender well location. I don't see the need for the Moroso disconnect switch with the additional terminals if the main power supplied to the alternator is coming directly from the new distribution block, which is basically replacing the relocated starter solenoid. The disconnect switch interrupts positive voltage power to the solenoid, the ignition signal wire, the starter, as well as the distribution block, which also supplies power to all accessories, EEC, etc. This should effectively turn everything off in the entire system.

As far as the ground from the battery to the engine block, I don't feel is necessary in my car, as I have welded subframe connectors, and will be receiving a roll cage. Right now I have the battery ground going to a 3/8" bolt through cleaned bare metal existing hole in a body brace inside the trunk, and another from the body brace to the quad shock mount on the frame rail.

 

[90sickfox]

@Knowbody
If the alternator is wired directly to the other wires it will power everything on its own. The way to test alternators in the 80s was to disconnect the battery. If it kept running the alternator was good.

The safety kill switch is so that in the event of a crash someone can locate and kill all electrical power to the vehicle. The way you're wired it would not cut off unless you turned the ignition switch off.

The starter pulls so much amperage that it only right to ground the battery directly to the engine block.

Alot of things have worked for me....like not using relays to turn on loads. It was fine....I just replaced the switches with burned contacts every year or so.

This is solid advice....and if he doesn't race then setting up power like yours is fine, provided there is a fuse or breaker in the power line running from the battery. Those things will burn in an accident. His ground ( and yours ) should be at the block. Have you done a voltage drop test on your car yet ?

 

[CarMichael Angelo]

My car has the 3G alternator installed, running for over a year with no issues, with the main power being fed off the solenoid in the stock fender well location. I don't see the need for the Moroso disconnect switch with the additional terminals if the main power supplied to the alternator is coming directly from the new distribution block, which is basically replacing the relocated starter solenoid. The disconnect switch interrupts positive voltage power to the solenoid, the ignition signal wire, the starter, as well as the distribution block, which also supplies power to all accessories, EEC, etc. This should effectively turn everything off in the entire system.

As far as the ground from the battery to the engine block, I don't feel is necessary in my car, as I have welded subframe connectors, and will be receiving a roll cage. Right now I have the battery ground going to a 3/8" bolt through cleaned bare metal existing hole in a body brace inside the trunk, and another from the body brace to the quad shock mount on the frame rail.

You should listen to this old guy,...^^ You asked for advice,...you've gotten it. Just because you've been doing it before doens't mean it was right. I've came across several friends that think a 12v switch w/ a fuse dongle attached is enough to interrupt/power a high current draw device, and fought me when I told them to put a damn relay in the circuit to avoid overheating the device myself several times..." But it's been working fine,....why do I need that?". This guy has helped more people, through more electrical problems than you'll ever want to encounter in your lifetime. But,......what do they say about horses and water? If you don't feel that the solutions to electrical advice you've solicited is/are necessary, than by all means,...full steam ahead...

Let me give you a link before you proceed.

http://www.stangnet.com/mustang-forums/forums/fox-5-0-mustang/

 

[a91what]

Yeah I have welded subframe connectors two batteries in the trunk 1/0 welding cable. Batteries grounded in the trunk. I had terrible hot start issues Chase my tail for months. I finally fix that issue by listening to what @jrichker had in his write up. As soon as I added that ground from the batteries to the block all of my issues went away

 

[Knowbody]

@jrichker @Chuckman @90sickfox @madmike1157 @a91what

You made me aware of something I completely missed. I should have known this on my own, and should have seen it in the diagram that jrichker posted originally. I did not account for the alternator powering the rest of the system. I am literally slapping my forehead right now, and I'll take that embarrassment deservedly. That being said, thanks for opening my eyes, I'm ordering the damn Moroso switch tonight!

 

[Nightstang00]

Would it be possible to use a cut off switch with just 2 posts vs the 4 moroso switch. Could I just put the alt wire and battery cables on the same post for it to provide power and shut off power ?

 

[jrichker]

Would it be possible to use a cut off switch with just 2 posts vs the 4 moroso switch. Could I just put the alt wire and battery cables on the same post for it to provide power and shut off power ?

What I posted is the way to do it right. I know it works and there are no stray paths for the alternator to get field power that would cause it to continue to output power.

 

[Nightstang00]

What I posted is the way to do it right. I know it works and there are no stray paths for the alternator to get field power that would cause it to continue to output power.

I appreciate your response, the only reason I ask is because I have the one with 2 posts already installed.