15 Year Member
Jul 13, 2003
Tucson AZ
Ok at first i blew my 150amp fuse for the battery, then i blew 2 kill switches (battery in trunk) . So now when i try to start the car it makes the click click sound like a dead battery does. So i check all the wiring and grounds and they look fine! The one ground on the passengerside motor mount is missing cause i ripped it off when pulling the motor. So i check the power with a volt meter on the + & - of the battery on the post's themselfs and i get a 11.6 reading. Then i check it at the starter solinoid and get the same this is done with the key off. So i try to start it and it click click click like a dead batter again and all my dash dummy lights go very dim and the fuel pump barely has enough juice to cycle, i instantly get out check the volts at the battery and get like 6 or 8 something? Then run to the starter solinoid and get about the same as the battery this is done with the key on with these readings? So i turn the key off and go back to the battery and can see the volts slowly starting to climb back up to the 11.6. What the hell can this be???????????? Could it be my ignition is going out or has gone out? peace

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John, what was the cause of the short in the first place?

Once you feel all the cables and E-system are ok, I'd charge the battery up. Even 11.6 volts is horribly discharged (and almost useless for a trunk-mount battery). When you connect the battery cables, be on the look-out for cables heating up real quick.
Knowing the cause of the original issue will help.

Good luck.
John, what was the cause of the short in the first place?

Once you feel all the cables and E-system are ok, I'd charge the battery up. Even 11.6 volts is horribly discharged (and almost useless for a trunk-mount battery). When you connect the battery cables, be on the look-out for cables heating up real quick.
Knowing the cause of the original issue will help.

Good luck.

I have no clue what caused it in the first palce? All i know is i hide all the wireing and put the battey in the trunk. Then a few months later it started turning over slowly then all of a sudden it blew the fuse. So i took the fuse out ad bypassed it, Then the switches. So 11.6 isnt a good battery? I have one of the optima red top's in there. What is a good bad reading then 12volts? Or more? oeace

A good 100% charged battery will read 13.1-13.2 volts. (2.2 volts per cell x 6 cells). I just measured mine and my DVM says 13.12 volts.
All my wireing is in good shape, nothing loose. I checked the battery and without the terminals hooked up i get high 12 readings. So i hook up the terminals and get the 11.6 or so again. Then turn on key and it goes down around 6-5. Turn key off again goes back back up to 11.6. Then i jumped it with my other car and got it started and i'm charging fine at the battery and the gauge on the dash say's so also. I turn it off hold the charge at the battery and starter solinoid for a couple minuets. Then turn key on and it's back to the same ol thing draining it!? I then hooked the kill switch back up for the hell of it and get the same reading's with the key off and on? So with or without the kill switch hooked up as soon as the key is switched to the off position it slow climb's back up to mid 11's but as soon as it is switched on it drops?Could it be a bad ignition switch? What could be comming on with the key to drain it that fast? I dont have a radio and there is no options on the car. I have a spare ignition switch so i might swap that today? Please any ideas from anyone else?! The only thing that i can hear when i turn on the ignition is the fuel pump sysle, so i unplug that and it still drains it? BTW thats the readings i get also without the terminals hooked up to the battery. peace

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

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

Wire the battery to the two 1/4" 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 1/4" 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 power
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

Fuel, alternator, A/C and ignition wiring

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

Vacuum diagram 89-93 Mustangs
You need to let the battery become fully charged to tell if its okay or not. Just jump starting it is not going to show anything. You need to disconnect the battery and let is charge slowly with a 2-10 amp setting on a battery charger. Like mentioned a fully charged battery should read 13.2 volts or so with the charger disconnected. The first thing you should do is find the short that caused you to burn the 150 amp fuse. If you just bypassed the fuse you could still have the short somewhere. This short could also drain/damage the battery.