Battery Relocation Ground Opinion

Fordfreak93

Mustang Master
Mar 12, 2009
264
273
84
Mooresville, NC
So my car is currently under construction with bits and pieces scattered all over the garage (it never ends)! The battery has been relocated to the trunk and is grounded to the body with another ground running back up to where the engine will eventually be. The motor is out while I paint the engine bay and install the K-member. I need to roll down the windows to install new guide bushings and run channel weather stripping. Can I can power the car on with just the body ground? I'm not trying to start it or anything, just need to power it up to roll the windows up and down. I'm leaning towards yes, just wanted a second opinion.
 
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Audiophile

Well-Known Member
Sep 9, 2013
202
48
59
48
Southern CA
I have never done exactly what you are describing. However, as long as its a solid ground (I like to ground to the frame itself), based on my electronic/electrical experience, I don't see any issue with it. Even when the battery is in its normal location, its grounded to the car. You will read ground with a meter whether its in the trunk or whether its up front. I'm sure you know this, but I just like to be clear in my explanations, so whoever reads it can put it all together.

Maybe this helps. Good luck working on your car!
 

Bullitt347

man bewbs please...
Mar 23, 2007
2,199
1,006
184
Pacific NW
When I installed the battery in the trunk of my car, ( mounted right rear) I ran the battery ground cable from the negative post thru the trunk floor and straight to the bolt that used to mount the quad shock to the frame. I did not run a cable forward to the engine. I ran a ground strap from the block to the frame, that is until I ran solid engine mounts, now there is no need to run the ground strap on the block anymore as it is directly grounded to the frame.
 

jrichker

StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
27,406
2,851
234
74
Dublin GA
lowendmac.com
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.


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.



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
 

SabinStangs

New Member
May 21, 2009
8
0
2
North Cackalacky
Thanks @jrichker. I was planning on running a ground wire from the body ground back up to the engine block, just didn't know if I could turn the ignition power on to roll down the windows without the engine ground in place yet.
 
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