Charging System Prob

[DocG]

Hey all.

First, I have a rear located battery, stock size alternator, and a somewhat built motor. The rear located battery is grounded to the body only in the back....and appears to have the proper size wiring for everything.

Before, the battery gauage would drop at idle, figured it was just the engine build being a bit much for the stocker. Last trip, the battery light came on and the gauge sunk. You could feel the loss of power at high rpm's as it wasn't getting enough spark or something.

So....time for a new alternator I'm guessing? Time to upgrade to 3G??


I realize the battery ground probably needs to be tied into the grounds up front, block/firewall/frame correct?

I also need to install a battery cutoff switch which will tie into the alternator.

So it looks like I need to route some proper ground wires, route a wire for the cut-off switch to the alternator, and probably replace the alternator.


My real question is.....is there any way of knowing if its my alternator, or possibly just because its not all grounded properly?

Any tips on installing the battery cut-off to a 3G would be helpful. I saw the great tech article on instaling it to what seemed to be a stock alt.

Thanks!

 

[jrichker]

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..

The screwdriver points to the common body ground for the alternator, battery and computer.

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 - Engine Information 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

 

[DocG]

Thanks. Looks like I need to get a 1 guage wire to run the ground up to the block.


Will things differ much if I pick up a 1-wire 3G alternator? With this I was going to run the one wire to the solenoid as normal, and put in a 200amp inline fuse.

Will there still be a regulator harness on the alt to be able to connect my cutoff switch too?

Seems pretty straightforward with the cut-off switch. I got the Moroso one after the other thread I made about switches. I'm going to hide it behind a flip down license plate frame.

Now I guess I'll make a parts list.

1 gauge wire.....from rear battery body ground to engine block

4 gauge wire for alternator to solenoid, with 200 amp inline fuse

4 gauge wire.....engine block to body ground as pictured above

18 gauge wire for shut-off switch to alternator



I've seen reference to tying in the engine block ground to the frame somehow? If I follow what I just posted above....is that something else I should do?