Hatch/Trunk Mounted Battery Ground Location...

Coupe: Battery in the trunk, ground cable to the rear bumper, which is bolted to the rear subframe.

Up front, engine block bolted to firewall and front subframe (subframe connectors make the connection complete).

in the back, I welded a bolt to the floor plate of my roll cage. up front the block is grounded to the body in the stock locations.

should go to the rear frame rail then run ground wire to the front and then ground at block.

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 Moroso : Category Display
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 Ford Fuel Injection » How To Solder Like a Pro 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
Mustang FAQ - Wiring & Engine Info 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

rear quad shock mount

Battery in hatch, 3g, won't fully charge? (I think)

jrichker said:

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.

Click to expand...

I've sifted through 10's of threads and can't find or continually overlook is probably more like it but what i'm having problems with.
From what i've read from your posts I may have messed up on the wiring in regards to the orange/black wire or old main power feed. This had been cut at the alternator and tucked under the airbox. The Fuse link for the Sense Wire felt soft so I ran a new one from the alternator to the Starter Solenoid. Didn't really cure it. Even tried running the Sense Wire from the alternator back to the battery directly and it didn't make a difference.

I currently have a gremlin. The car is having trouble letting loose, if that makes sense. Feels like some type of electrical inference or ground issue. Just started a few months back. If I throw the charger on the car runs great but seems to slowly drain affecting performance. It's odd, I can't tell if the headlights dim or not but the car sounds like its suffocating without the full charge. Muffled not crisp at all.

Can't recall exactly but i'll try. To and from the battery, in the hatch, the really thick wire, "1-g I think?" The ground goes from the battery to the wheel well and from the wheel well it runs to the block. I'm using something on the passengers side that might have been used for old egr stuff or something for the ground location. From there I continue, now with a 4g wire to the "pigtail" where the old battery was. I also grounded the computer dedicated wire to the same spot on the block. The 02 wire is on the passenger head and not "loose or disconnected" along with the braided strap that I changed to a 4g wire.

91 GT I bought new.

Relocation kit used: http://www.summitracing.com/parts/TAY-48103/?rtype=10

Thanks

Ok, to the thread starter, save yourself the hassle and run a ground to the frame, and the block. I just fixed a problem with the help of jrichker, where my starter every 20-30 starts would stick and continue to run. I only had a ground wire to the rear frame and he told me to run a 2 awg cable from battery to block. Low and behold problem is gone!

Glad to hear it worked out for ya.
I suppose it couldn't hurt running an additional ground. Would like to see what jrichker suggests too.
Mine's a little different now that the battery is in the trunk, the oem alt. main power wire has been cut, the sense wire now wired directly from the alt. to solenoid, and even the org. ground position aside the water pump/timing chain cover is stripped and relocated.
It's closer, whatever the problem is. The battery holds it's charge ok as long as you don't run anything like the lights or blower.
Really could be as easy as adding another ground as you suggest.

Thanks.

U can use a ground strap from block to frame rail also

Hatch car. Ground is bolted to rear seat stud in the rear. I have a four gauge wire from the timing chain cover to a bolt for the sway bar and a replacement ground strap on the rear of the motor to the firewall. 3G upgrade and it works fine.

RangerJoe said:

Hatch car. Ground is bolted to rear seat stud in the rear. I have a four gauge wire from the timing chain cover to a bolt for the sway bar and a replacement ground strap on the rear of the motor to the firewall. 3G upgrade and it works fine.

Click to expand...

Battery to wheel well using 1/0
wheel well to block using 1/0
block to chassis/pigtail location between battery and solenoid using 4g.

ECC is grounded at block to chassis/pigtail

Also ground strap ground, head to firewall. Meets at head with o2 ground and runs to firewall. Strap is now 4g wire instead.

"Sense Wire" runs direct from alt. pos. to solenoid pos.
_____________________________________________________
NOTE: Do not follow this as advice on how to install! I'm here to figure out what I might have done wrong!

Billy88LX said:

rear quad shock mount

Click to expand...

Same here. I have the big cable off of the battery mounted there after hitting the area with a wire wheel to get it nice and shiny.

I also have the smaller (10 guage?) wire mounted on the top of the fender.

Beasty306GT said:

U can use a ground strap from block to frame rail also

Click to expand...

I have two 4 gauge grounding straps. 1 on each side going from between the motor mount and the block and bolted to the spot where the front sway bar mounts.

On my coupe, I ran a 4g ground from the battery to the small rail (with a bolt) below the trunk opening, and a second 4g from there to the frame rail (with a large sheet metal screw) right in front of the battery. The engine is grounded with the factory ground straps. On the positive, I ran a 4 g from the battery to a second solenoid mounted on the passsenger side, and tied the starter cable to the new solenoid. This shortened the run from the battery to the starter by several feet, enabling the use of the smaller 4g cable to save weight (combined with the mini starter to reduce current draw). I then ran a 4g wire from the new solenoid to the positive feed on the original solenoid (to get to the alternator), plus a 14g trigger wire between the solenoids to engage the starter. It's worked without any issues for ten years now. The 4g was too small to operate the original big starter, but with the mini starter it works perfect.

So many ways to skin a cat, lol.
So after my mistake in cutting the old main power fire, not reusing it and also now running the Sense Wire direct from the alt. plug to solenoid is ok as well as the way I currently have the car grounded?
I'm still having some issues and am trying to eliminate this part of it.
Battery is in the hatch.
Thanks again.

See my previous entry in this series of posts for the rear mounted battery ground and cutoff switch.


Alternator troubleshooting for 86-95 5.0 Mustangs:


Never, never disconnect an alternator from the battery with the engine running. The resulting voltage spike can damage the car's electronics including the alternator.

Do all of these tests in sequence. Do not skip around. The results of each test depend on the results of the previous tests for correct interpretation.

Engine off, ignition off, battery fully charged.
1.) Look for 12 volts at the alternator output. No 12 volts and the dark green fuse link between the orange/black wires and the battery side of the starter solenoid has open circuited.
3G alternator: Look for 12 volts at the stud on the back of the alternator where the 4 gauge power feed wire is bolted.
No voltage and the fuse for the 4 gauge power feed wire is open or there are some loose connections.
2.) Look for 12 volts on the yellow/white wire that is the power feed to the regulator. No 12 volts, and the fuse link for the yellow/white wire has open circuited.

Engine off, ignition on, battery fully charged.
1.) Alternator warning light should glow. No glow, bulb has burned out or there is a break in the wiring between the regulator plug and the dash. The warning light supplies an exciter voltage that tells the regulator to turn on. There is a 500 ohm resistor in parallel with the warning light so that if the bulb burns out, the regulator still gets the exciter voltage.
Disconnect the D connector with the 3 wires (yellow/white, white/black and green/red) from the voltage regulator.
Measure the voltage on the Lt green/red wire. It should be 12 volts. No 12 volts and the wire is broken, or the 500 ohm resistor and dash indicator lamp are bad. If the 12 volts is missing, replace the warning lamp. If after replacing the warning lamp, the test fails again, the wiring between the warning lamp and the alternator is faulty. The warning lamp circuit is part of the instrument panel and contains some connectors that may cause problems.

2.) Reconnect the D plug to the alternator
Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see 2.4-2.6 volts. No voltage and the previous tests passed, you have a failed regulator. This is an actual measurement taken from a car with a working electrical system.

Engine on, Ignition on, battery fully charged:
Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see battery voltage minus .25 to 1.0 volt. If the battery measured across the battery is 15.25 volts, you should see 14.50 volts

Familiarize yourself with the following application note from Fluke: See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. .


You will need to do some voltage drop testing of several of the wires.

Start looking for these things:
1.) Bad diode(s) in the alternator - one or more diodes have open circuited and are causing the voltage to drop off as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.

2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Do the voltage drop test as shown in the Fluke tech note link. Measure the voltage drop between the alternator frame and the battery negative post. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.

3.) Bad regulator that does not increase field current as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.

4.) Bad sense wire - open circuit in sense wiring or high resistance. The yellow/white wire is the voltage sense and power for the field. There is a fuse link embedded in the wiring where it connects to the black/orange wiring that can open up and cause problems. Disconnect the battery negative cable from the battery: this will keep you from making sparks when you do the next step. Then disconnect the yellow/white wire at the alternator and the green fuse link at the starter solenoid/starter relay. Measure the resistance between the alternator end of the yellow/white wire and the green fuse link: you should see less than 1 ohm. Reconnect all the wires when you have completed this step.

5.) Bad power feed wiring from the alternator. Use caution in the next step, since you will need to do it with everything powered up and the engine running. You are going to do the Fluke voltage drop tests on the power feed wiring, fuse links and associated parts. Connect one DMM lead to the battery side of the starter solenoid/starter relay. Carefully probe the backside of the black/orange wire connector where it plugs into the alternator. With the engine off, you should see very little voltage. Start the engine and increase the load on the electrical system. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.





Alternator wiring circuit
Notice the green wire connects to a switched power source. The circuit contains a 500 ohm resistor in series between the switched power and the alternator. Connecting it to switched power keeps the regulator from drawing current when the engine is not running. The resistor limits the current flowing through the wire so that a fuse isn't needed if the wire shorts to ground.

Also notice the sense wire connects to the starter solenoid and it is fused. The fuse protects the wiring if the regulator develops a short circuit to ground. It connects to the starter solenoid so that it can "sense" the voltage drop across the output wiring from the alternator.

1/0 from the battery straight up front to the engine block, from there to the swaybar mount.

chitownstang1 said:

If I throw the charger on the car runs great but seems to slowly drain affecting performance.

Click to expand...

I wonder what would happen if you left the charger hooked up but output off, then quickly switched it back on after it started running bad again?

chitownstang1 said:

The ground goes from the battery to the wheel well and from the wheel well it runs to the block. I'm using something on the passengers side that might have been used for old egr stuff or something for the ground location. From there I continue, now with a 4g wire to the "pigtail" where the old battery was.

Click to expand...

I'd run a dedicated ground from the block to front subframe. From your posts, it doesn't seem like the battery is grounded at all to the rear subframe. I don't suppose you have to but most guys, when battery's back there, the neg. terminal goes up front like yours, but is also connected to ground back there. Also up front, you're grounded to the front body, but not the front subframe. Sorry if I missed something

I have a notch with the battery in the trunk.

I'm leaning towards the battery charger thing as misleading. I typically will charge the battery while not connected to the car resetting the computer. Since ditching the charger theory/idea the battery is 12.+v every morning.

Key One Engine Off: I checked the LtG/R wire at the alternator and got 12.8v but when plugged in it was 3.8v?

I'll start drop voltage testing tomorrow. With the way the computer/car can run great then not that seem to coincide with the low oil and possibly the coolant dash lights, the slight buzz in the stereo, there's more to this but in a nutshell this really feels like some type of short.

It's fun to mess around with the Stang from time to time but this is starting to take it's toll. Countless hours and very few cruises this season, well, sucks.

Thanks everyone for your help.