Electrical 1988 Mustang 5.0 GT Charging Problems

BradyB1999

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Apr 10, 2022
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Hi guys! I'm sure we've all seen these threads about the alternator not charging properly. I've been through countless threads doing research as to why my Mustang isn't charging, and I finally got the time to do some tests. I'm aware of the step-by-step that has been floating around, but my problem isn't mentioned specifically in that so I figured I'd come and see what you guys thought.

I think it might have something to do with my voltage regulator? I bought a new 3G alternator (only 95amp so no modification needed). My 12v yellow wire is receiving full power. My green/red switched wire is receiving full power with key on (probing with the plug disconnected). However I got stuck on the second part of that step. In the diagnosis it states the voltage of that same green/red wire should be 2.4-2.6v when plugged in and probing from the back. It states if no voltage or too high of voltage the regulator has gone bad. My voltage probing from the back shows 1.36v which is much lower than the 2.4v suggested, but it's also not 0 like some others with that problem.

Again the alternator is new not reman, and so should that voltage regulator. Could the regulator still be bad if it's showing voltage, just not enough? The battery is new as well. I'm trying to sell the car but the battery not charging is being a huge turn-off for buyers.
 
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BradyB1999

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Apr 10, 2022
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Hi good question. Yes I had to splice in a new connector for the pin, but it appears to be so. I mean it could be broken in between the tape, but doesn’t look to be
8270EF06-7909-4052-81EB-8A17D297F9A9.jpeg

What about the white wire ? Does it go from the 3 wire connector to the single wire pin on the alternator body.
 

79pace

something stupid will fall out of my mouth
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Jul 21, 2000
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You really need to run the one single heavy gauge wire over to the battery side of the car. I have read some horror stories of guys burning their cars down keeping the two wire setup. And when I did my upgrade I never saw 14 volts from the alternator until I put the Yellow wire directly on the post on the back of the alternator for it to see voltage, then I got 14. Before that it was putting out 11. something. Maybe not ideal but it worked. Do you have 14 coming out of alternator now?
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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You didn't happen by chance to change out the AMP light bulb in the dash to an LED?

The voltage regulator is fed from the cluster, and if this bulb is missing, or swapped to an LED it wont work right
 

BradyB1999

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Apr 10, 2022
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You really need to run the one single heavy gauge wire over to the battery side of the car. I have read some horror stories of guys burning their cars down keeping the two wire setup. And when I did my upgrade I never saw 14 volts from the alternator until I put the Yellow wire directly on the post on the back of the alternator for it to see voltage, then I got 14. Before that it was putting out 11. something. Maybe not ideal but it worked. Do you have 14 coming out of alternator now?
That’s good to know. Even through the instructions said it want necessary it might just be worth doing. I haven’t measured voltage out. When the car is running that would be the bottom post with the black wires that would tell me output?
 

BradyB1999

New Member
Apr 10, 2022
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You didn't happen by chance to change out the AMP light bulb in the dash to an LED?

The voltage regulator is fed from the cluster, and if this bulb is missing, or swapped to an LED it wont work right
The gauge actually was replaced with a 4 cylinder dash at one point in its life. But I do know that I don’t get any alternator warning light at all when I turn the key. But it still shows full battery voltage for the switched wire (green/red)
 

79pace

something stupid will fall out of my mouth
Founding Member
Jul 21, 2000
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That’s good to know. Even through the instructions said it want necessary it might just be worth doing. I haven’t measured voltage out. When the car is running that would be the bottom post with the black wires that would tell me output?
Yes, I hooked the trigger wire to the main output post and finally got 14 volts. I bet your only getting 11 from the back post right now. Move that wire and see if it goes to 14.
 
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BradyB1999

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Apr 10, 2022
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Yes, I hooked the trigger wire to the main output post and finally got 14 volts. I bet your only getting 11 from the back post right now. Move that wire and see if it goes to 14.
Alright I’ll give it a shot! Earlier you said yellow wire to the post. Are you talking about the yellow wire coming off of the 3 prong D plug being the trigger wire? I'm just trying to visualize it here. Do you by chance have a reference photo? The way I read it, it's basically a straight shot from the 3 plug to the post.

And as far as the horror stories lol... I've been digging into it and have read that the two wire setup is a curse as well. So maybe just disconnect the two black wires and replace with a 4 gauge straight to starter relay?
 

KRUISR

5 Year Member
Apr 16, 2015
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Yes ditch the 2 power wire set up back to starter solenoid. A simple source for the 4 gauge power wire is the 99 and up Windstar and 04-07 Freestar minivans. Their alternator is on passenger side as well, they use a 135A 6G alternator and have the power going directly from alternator power bolt to battery post (battery side of starter solenoid is the same). That's what I did with mine.
 
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BradyB1999

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Apr 10, 2022
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Hi guys. I was just about to go to the hardware store to get some wire when I decided to start her up again after a couple weeks. Sure enough, getting 14 volts. Im not sure why or how, but it’s charging again. Will definitely have to do the wire upgrade still, but it’s working again thanks all. So weird
 

CAMTWO1070

Active Member
Dec 17, 2021
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You might have an EEC issue as alternators are controlled by the EEC but I strongly feel the alternator body isnt properly grounded but looking at the picture it seems sorry to say the whole alternator is installed;- Mostly wrong.....

For those who think the EEC has no bearing on charging heres a snapshot...

Screenshot 2022-04-17 165123.jpg


To do the job right you should of totally did away with everything from the side of the alternator to the battery and ran a solid 4 ga fine strand welding cable with a copper lug attached and hooked it direct to the battery with a same amperage fuse...Those split power coarse copper wires are gonna melt and start a fire........

You can get a 3ft 4 ga battery cable with copper lugs on both ends for $10 bux at AutoZone

Butt connectors are never a good idea when bumping up the amperage...I solder all my connections with silver solder and use shrink wrap..

Another thing you needed to do was to totally remove the alternator bracket from the engine and clean up where it mates together with the engine block and to clean up the slider joint that tightens the alternator with side pressure too as these are the alternators ground path..

Good grounds are important...I run my grounds from battery to engine block , engine block to frame and engine block to starter then battery to core support

This pic os an old pic before I did the 3g alternator upgrade but have crappy pics of the process too...

IMG_20201209_123730174.jpg


Plus the alternator body has a screw on the back that needs a dedicated ground going from the alternator body to the battery negative cable or the battery frame too..

Heres a crappy shot,,,The baby blue shrinkwrap is the alternator body ground...


The thick red going to the supersized battery terminal is coming from the alternator.....I have pics w/ the noise filter somewhere..LOL

IMG_20210903_121015.jpg


I have my negative coming from the alternator going to the sidescrew on my NewMar alternator noise filter I have installed between the alternator and the battery with the noise filter body grounded to the frame..My tuner says in all of his years tuning EEC systems mine is the most stabile with way less interferrence and noise spikes..

Good Luck
 

CAMTWO1070

Active Member
Dec 17, 2021
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In addition to eliminating noise and errant voltage spikes I use some simple clip on devices called ferrite bead Chokes and I also invented my own system aswell

It seems anistropic crystals filter out EMI radiation and R/F interferrence so I made my own grounding system that pulls the pollution out of the system and neutralizes it...............LOL

Its been a breakthrough discovery since 2016 and talk amongst the quantum physics crowd since the because it took means of destructive methods to neutralize them before....LOL

IMG_20211221_023654.jpg


Theres alot more than meets the eye with these hand fabbed copper busbars...Inside each is a meld of smelted precious metals with precise percentages only known to me and soon after approval will be standard equipment in veryday vehicles to eliminate people from the harm of radiation.........

What most dont realize is that standing too close to that harmless looking alternator isnt so harmless...With my system it is....LOL
IMG_20211221_034901.jpg


IMG_20211221_152627.jpg


Good Luck and take care..
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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In addition to eliminating noise and errant voltage spikes I use some simple clip on devices called ferrite bead Chokes and I also invented my own system aswell

It seems anistropic crystals filter out EMI radiation and R/F interferrence so I made my own grounding system that pulls the pollution out of the system and neutralizes it...............LOL

Its been a breakthrough discovery since 2016 and talk amongst the quantum physics crowd since the because it took means of destructive methods to neutralize them before....LOL

IMG_20211221_023654.jpg


Theres alot more than meets the eye with these hand fabbed copper busbars...Inside each is a meld of smelted precious metals with precise percentages only known to me and soon after approval will be standard equipment in veryday vehicles to eliminate people from the harm of radiation.........

What most dont realize is that standing too close to that harmless looking alternator isnt so harmless...With my system it is....LOL
IMG_20211221_034901.jpg


IMG_20211221_152627.jpg


Good Luck and take care..
there is a lot going on there that is above my pay grade.