Engine 3G alternator ground questions.

91GTstroked

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Jun 14, 2007
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Hope everyone is doing well!

So, am I crazy for wanting to put my battery back in the engine bay?

My car is strictly a cruiser. I already have a PA 3g alternator on the car with upgraded grounds.

Right now I have a 4 gauge ground going from engine block to the frame. The engine side is normally where the battery negative cable attaches to. Can I still run the negative battery cable to that same location with the 4 gauge ground on there? Or do I need to move the 4 gauge ground somewhere else?

Thanks.
 
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jrichker

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Hope everyone is doing well!

So, am I crazy for wanting to put my battery back in the engine bay?

My car is strictly a cruiser. I already have a PA 3g alternator on the car with upgraded grounds.

Right now I have a 4 gauge ground going from engine block to the frame. The engine side is normally where the battery negative cable attaches to. Can I still run the negative battery cable to that same location with the 4 gauge ground on there? Or do I need to move the 4 gauge ground somewhere else?

Thanks.
Rear mounted battery wiring recommendations

For a battery cut off switch, see https://www.moroso.com/catalog/pro...rnator-disconnect-switch74108/category/3114/
is the switch
https://www.moroso.com/pub/media/instructions/74108_instweb.pdf is the installation instructions.
Switch picture...
Morso battery cutoff switch.JPG


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 in 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[/QUOTE]
 

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91GTstroked

Active Member
Jun 14, 2007
203
56
38
Guys the battery is all ready in the trunk. I want to move it back up in engine bay!

I believe the only extra ground is the 4 gauge wire from block to the frame.

I want to know if I can put the negative battery cable on the same place as the 4 gauge ground wire? Which is in the factory location for the negative battery cable.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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Ok, I think it is in the 'no start checklist' that gives you ground locations, check the resources page, battery ground to block, this is the bolt on the timing cover, battery ground to inner fender panel between the battery and the solenoid, that is a computer ground, firewall to drivers side head, this is the ground for the instrument cluster. Some add a block to chassis ground for 'piece of mind'.
 
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KRUISR

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Apr 16, 2015
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I can put the negative battery cable on the same place as the 4 gauge ground wire? Which is in the factory location for the negative battery cable.
If I am reading this correct, you want to attach the battery negative to the same bolt as this non-original engine block to chassis ground was installed.

I would say there is no issue having both cables on the same bolt on the engine block. Just make sure the connections are good and clean to maintain current flow.
 
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91GTstroked

Active Member
Jun 14, 2007
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If I am reading this correct, you want to attach the battery negative to the same bolt as this non-original engine block to chassis ground was installed.

I would say there is no issue having both cables on the same bolt on the engine block. Just make sure the connections are good and clean to maintain current flow.
That is correct. I have the upgraded 4 gauge wire going from timing chain cover to the frame. I'd like to attach the negative battery ground to the same bolt on timing cover.
 

KRUISR

Active Member
Apr 16, 2015
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If you think about it, what you are asking about is essentially the factory grounding set up and you added an extra ground from engine to chassis (normally there is one on the back of drivers side cylinder head or trans bolt to firewall).

Extra ground wires connecting engine to chassis are not a problem. Will help if you have an issue with a factory ground wire somewhere.

My negative battery cable has 2 wires, one to the timing cover bolt and a smaller one to the bolt on inner fender beside/behind the battery (shown in pic in post #4 - with screwdriver pointing at it).
 
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Blown88GT

Founding Member
Nov 13, 1999
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If you think about it, what you are asking about is essentially the factory grounding set up and you added an extra ground from engine to chassis (normally there is one on the back of drivers side cylinder head or trans bolt to firewall).

Extra ground wires connecting engine to chassis are not a problem. Will help if you have an issue with a factory ground wire somewhere.

My negative battery cable has 2 wires, one to the timing cover bolt and a smaller one to the bolt on inner fender beside/behind the battery (shown in pic in post #4 - with screwdriver pointing at it).
I think that's the TFI shield ground.
 

7991LXnSHO

Now I want a 10 year badge
Sep 1, 2010
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If the car is a cruiser, I would not like the battery taking up any space in the little trunk or hatch area the car has. Got to have room for the subwoofer box or keg.
No, you are not crazy.
 
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7991LXnSHO

Now I want a 10 year badge
Sep 1, 2010
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I gave up on getting a pro haircut two weeks ago. (I already needed a haircut at the start of March) and used the electric trimmer. I will not be mistaken for a Karen Or Beethoven for months now. It looked like I committed Hairy-Carry.
Now what were we talking about?
 
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