92 mustang gt problem with charging system

kneith · Jun 5, 2009

I have a problem with charging system on my 92 gt
i have a new alternator in car
went to autozone tonite to have system checked
and car is not charging one bit
i just bought this car, and noticed when car is running
dash lights are on and parking lights automatically come on
as soon as you start car.
and they stay on when car is running
also battery light comes on in car and stays on
and amp gauge just stays right above 8 no matter what
any ideas what could be the problem
i am gonna take alternator off tomorrow and have it checked
of course the owner before me bought it at autozone
i am just worried about the lights coming on as soon as you turn key on

Turd Tops · Jun 5, 2009

Is it charging "not one bit" or is it charging at 8 volts?
Do you have underdrive pullies on it? The lights should not be coming on unless somebody installed daytime running lights.
Does the car still run for long or does it die after a bit? Also will it restart after you shut it off or does it need a jump everytime?

jrichker · Jun 5, 2009

A 92 Mustang does not have an amp gauge. All the 87 and later cars have a voltmeter. The 8 is 8 volts, which shows a very low battery.

Make sure the battery is up to full charge. It is needed to provide power for the alternator regulator and field windings. If it is too low, the alternator will not charge properly.

Have the alternator checked out of the car for sure.

Then look for other problems...
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.
Any car that has a 3G or high output current alternator needs
a 4 gauge ground wire running from the block to the chassis
ground where the battery pigtail ground connects.
The 3G has a 130 amp capacity, so you wire the power side
with 4 gauge wire. It stands to reason that the ground side
handles just a much current, so it needs to be 4 gauge too.

The picture shows the common ground point for the battery & extra 3G
alternator ground wire as described above in paragraph 2. A screwdriver
points to the bolt that is the common ground point.
The battery common ground is a 10 gauge pigtail with the computer ground
attached to it.

Picture courtesy timewarped1972

Lawbreaker5.0 · Jun 5, 2009

do you live in canada? or is the car from canada? cuz i've only heard the daytime running lights were from the canadian 5.0's

sounds like the alternator is not working what so ever. i would check the wiring. back to the solenoid, sounds like you have a short. Might as well run new 4 guage wire any way.

Lawbreaker5.0 · Jun 5, 2009

do you live in canada? or is the car from canada? cuz i've only heard the daytime running lights were from the canadian 5.0's

sounds like the alternator is not working what so ever. i would check the wiring. back to the solenoid, sounds like you have a short. Might as well run new 4 guage wire any way.

kneith · Jun 6, 2009

ok 92 mustang gt charging problems

ok thanks for the replies guys
let me answer some of your guys answers
ok the gauges in the car arent working at all
but the alternator and battery were tested and they passed
the lights that are coming on when the key is turned on are not running lights at all, so here we go with what i have found out so far
i started checking fuses # 13 i am getting a reading of 10 & 10 volts
# 15 is 0 & 0
#16 is 12 & 0
the other thing i am having trouble with is
where is the motor starter relay located
is says to check fuse there also
but i cant find that or what it is
thanks

HISSIN50 · Jun 6, 2009

On the regulator are terminals A, S, I.
A should show battery voltage.
S should float about 1/2 battery voltage while the car runs and the alt functions.
I should show 2+ volts while the battery light is illuminated.

The charge cable has a couple of links that should be checked, and the A circuit has a link (in case A shows no voltage).

Lawbreaker5.0 · Jun 7, 2009

kneith said:
ok thanks for the replies guys
let me answer some of your guys answers
ok the gauges in the car arent working at all
but the alternator and battery were tested and they passed
the lights that are coming on when the key is turned on are not running lights at all, so here we go with what i have found out so far
i started checking fuses # 13 i am getting a reading of 10 & 10 volts
# 15 is 0 & 0
#16 is 12 & 0
the other thing i am having trouble with is
where is the motor starter relay located
is says to check fuse there also
but i cant find that or what it is
thanks

there are fusable links that come off the starter relay. They look like regular wires. check voltage through those wires. THe relay should be mounted on the driverside fenderwall, by the battery

kneith · Jun 7, 2009

does the car need to be running or just in the run position to check the voltage

kneith · Jun 10, 2009

92 mustang charging problem

Ok I checked the plugs on the alternator, and here is what i am getting
the alternator rectifier plug there is a white with black strip wire
that goes from rectifier plug directly to voltage regulator plug
i get no volts on either end of that plug or wire with car on and running
or just with the key in run position i get no volts
the other wires i do get 6 volts on one wire
and i get 12 volts on the other wire
is there anything wrong with these two plugs or is that normal
thanks for any help in advance

kneith · Jun 11, 2009

ok my bad sorry about the new thread kinda new to this forum stuff
well anyway, my fault when alternator was on car and tested
IT DID NOT PASS.................
But when i took alternator off of car it did pass on their machine inside autozone
and battery passed as well.
the alternator that is on car was purchased of course at Autozone
the previous owner bought it from there and it is only a 75 amp alternator
is the alternator ok to use on this car that is what they gave him?
and I checked the Voltage Regulator Plug with key at ON position
A is 12 volts
S is 0 volts
I is 6 volts
and with car running i get the same readings

HISSIN50 · Jun 11, 2009

Testing needs to be done with the car operating.

What is the ASI reading while it idles?
What is the battery voltage while it idles and at 2K RPM?

kneith · Jun 11, 2009

ok i have checked the volts again at IDLE and at 2k rpms
A=12, S=0, I=6 at idle

A=12, S=01 I=12 at 2k rpms

what does this mean? is this good or bad

kneith · Jun 11, 2009

oops sorry a revision here on the I value was at 12 at idle

ok i have checked the volts again at IDLE and at 2k rpms
A=12, S=0, I=12 at idle

A=12, S=01 I=12 at 2k rpms

what does this mean? is this good or bad

90limited · Jun 11, 2009

you mentioned that the gauges are not working...? All of them or just the volts? If the volts is reading 8 maybe the battery is so low that is what you get. Put a battery charger on and see if the gauge goes up.

I had a charging problem after an interior resto. I damaged the back of the gauge panel foil that went to the volts gauge. The alternator has an exciter circuit that goes to the idiot light on the dash. If that circuit is bad or the alternator is bad it make the light on the dash come on. I had to repair the foil on the gauge cluster with a jumper wire and it fixed my problem...

Good luck.

Simple88GT · Jun 11, 2009

I had this same problem last year, and what ended up being the problem was the other plug, the smaller one, on the alternator, the green red wire was not getting a good connection, and that wire is the one that tells the alternator to charge.

On a side note however it sounds like you have some other issues with the wiring to the dash i would try to get that fixed and then work on getting the alternator working cause the two could be related.

-Josh-

kneith · Jun 11, 2009

thanks for the responses
the volt gauge and oil pressure gauges are the ones that kind of work
volt gauge is always at 8 and the oil pressure gauge is right in the middle
right now them are the only 2 that i have problems with
sometimes they work and sometimes they dont........lol
but the rest of the gauges are fine
do i pu tthe charger on the battery while the car is running
or just in the on position?

kneith · Jun 11, 2009

what did you have to do to fix that wire that makes it charge? do i just buy the voltage regulator plug and cut the old one off correct?

Simple88GT · Jun 11, 2009

yeah i went to autozone and it was fairly cheap cut off the old one and soldered the new one in place, charges better than before because it actually keeps charging. the alternator I have is and 80 amp off of an f150 that the previous owner put on. when this one goes i will be putting a 3g on. but it work fine with what I have, I have upgraded all of the wires though, I have 2 gauge charge wires.

kneith · Jun 11, 2009

oh kool, thanks i will be doing that next
so i need to solder the two ends together though
i just bought this car last week from a guy who needed money it is in really good shape
i need it had some gremlins i am just trying to get it to charge right now
thanks.............will splice connectors be enought or should i solder them?

92 mustang gt problem with charging system

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