I have a 93 splash with the 4.0 and a 5 speed. If love could be described I would easily compare it to how I feel about this truck. To the point, I have a good ALT that does not charge the battery. RPM does not matter in this, I can have it red lined and the alt does not kick up the charge. I have already rebuilt the positive and negative wires to the battery (from starter up). It was doing just fine (or so I think) until today. I drove it to work, went on break (3 miles of travel each way), and then went out to my shop to put rims on. As I got close to home I realized that my lights were dim, this trip is about 10 miles. I got into my home garage and started testing everything with my multimeter. I have (with the tender on) 12.5 volts at the terminals. Further testing in this situation leads to 12.5 at the solenoid. I tested at the alt and I have 12.4 at the alt. I forget the color of the wire but it was the closest to the single separate wire clip. The far left wire? Motor running I pull less volts (at the batt) then off. I tested the alt and it hit a max of 16.2 and a low of 13.2 volts. Now after shutting off the truck my battery voltage climbs back to around 12 (depending on how long I drained it). I would love to say that my battery is bad. It is a new battery, but I dont put to much stock into (new batteries). I'm more worried about my power wires rebuild and what that may be doing. I'm lost. I really want to drive this damn truck.

 

Welcome to the forum

First a little Alternator 101

An alternator has an ON/OFF switch
An alternator NEEDS power to start making power.

So this is not a "chicken and egg" thing, alternator must have 12volts to start with or spinning it at any RPM won't matter, it can't make power without having power first.

But if you give an alternator power all the time it will drain the battery as it sits, so there has to be an ON/OFF switch to give the alternator "startup power" when you need it.

This ON/OFF switch is the Battery Light circuit.
Turn on the ignition key, do you see the Battery Light ON, if not then alternator can not work.
Battery light circuit often has its own fuse in the Cab Fuse box, or it may be shared with another circuit but there WILL be a fuse in the cab fuse panel.
So no Battery Light = no alternator

Battery Light circuit will be the Green wire on the 3 wire connector on the alternator, with Key ON this Green wire should have 12volts(battery voltage)
Key OFF no 12volts on this Green wire
Pull off connector and test that

Also while connector is off test the Yellow wire, it should have 12volts all the time, key off or on won't matter.
If no 12volts then check the engine fuse box for Alternator Fuse 15amp, it is blown, no power on the yellow wire will also prevent alternator from working.


Working alternator will do this:
After start up of the engine battery voltage should be 14.6 to 14.9volts, under 15volts
That is the "recharge voltage" to build battery charge back up after it was drained by starter motor.
That should last about 5 minutes or so, depending on the battery.
After that the voltage at the battery should drop to 13.6volts, this is the "maintenance voltage", the 14+ volts will cook the battery over time so voltage needs to drop down to avoid that.
After battery voltage is at 13.6v and engine is idling, turn on the headlights, fan blower to high and anything else that is electric, check voltage, it will drop each time something is turn on but should come back up to 13.6v.
This is the Voltage regulator in the alternator working like it should, it sets the Recharge voltage and maintenance voltage, it also monitors voltage to keep it at 13.6volts.

If voltage drops below 13.4volts at idle with all electrics on then your alternator has 1 failed Field, it has 3 so 1 failed field is OK for now, but time to shop for alternator sale, lol.

I.E. dimming headlights at idle means 1 failed field in the alternator, assuming alternator is working otherwise

 

The yellow wire has 12 volts at off. I do have a battery light before i start the truck. I have 6 volts on the wire in the single clip (wire that is all by itself). I have not checked the green wire as of yet. Now once the truck is running I lose battery power pretty rapidly. My battery ticks off .01 volts pretty rapidly, but when the truck is off the battery holds power.
Say i have 12.5 with the truck off at the battery. Once i start the truck, I am down to 11.66 immediately and after that I drop volts at the battery pretty quickly. I did have the alt tested at my local O'riellys and it put out a max of 16 volts and a low of 13.9. It passed its test with flying colors. I will go check the green wire with the key on.

 

and thank you for the alt info. It will be referred to timelessly

 

yea i have 12.44 volts on the green wire with key on.

 

You said earlier that you checked the B+ terminal on the alternator and had 12volts?

B+ is the where the larger wire connects to alternator, usually a Black/orange stripe wire.

This wire sends the alternator power to the battery, it should show 12volts all the time, key on/off doesn't matter.
In 1993 models it is connect to the battery via a Fusible Link, in this case a Dark Grey wire.
If you don't show full 12volts on B+ wire then that is where the problem is.
B+ wiring is like this::

Alternator B+-----(black/orange wire)--------(Dark Grey wire/Fusible link)------(Red wire)------Battery positive

So the fusible link is spliced between the B+ wire and battery wire

A fusible link acts as a Slow Blow fuse, if it heats up from a short or too many amps(same as a short) then it will separate(blow) without starting a fire.

Google: fusible link images
To see what they look like, just a short wire really, but a very important short wire.

Just to sum up:
B+ wire, 12volts all the time(fusible link or Maxi-fuse)

3 wire connector
Green wire, 12volts with key on only(battery Light wire)
Yellow wire, 12volts all the time(15amp fuse or fusible link)
White jumper wire, stator wire, usually 1/2 battery voltage so 6volts

 

You mean the wire connected to the rear of the alt with a 10mm bolt? I haven't checked it yet.

 

Yes, that is the alternator's Output voltage that goes to the Battery and also whole truck electrical system.

I thought you had tested it from this: "I tested at the alt and I have 12.4 at the alt"

One other thing, put volt meter's Black(ground) probe wire on alternators metal case, and put Red probe on Battery's Positive terminal, should read 12volts, you are testing that alternator is Grounded via bolts to the engine block and good Battery Ground cable.

 

It reads super high at like 28volts. My stator wire also reads very high. I was wrong before. Also I had my radio out. The original clips were gone and I had power to the radio but no sound so I investigated. Once I re hooked up the radio I can maintain voltage at around 12 but it doesn't charge. Once I shut the truck off my voltage climbs back up quite a bit

 

Alt is grounded correctly. I got the same reading positive to alt housing as pos to neg

 

There is nothing in the vehicle that can make voltage higher than battery voltage with engine off, so there is something wrong with meter settings.

If you saw 28volts with engine running then you have/will ruin the battery, and fry many electrical parts in the truck.

All testing of alternator is done with engine OFF

If all 4 wires at alternator test OK, then reconnect all the wires.
Then you can start engine, from then on you only test at battery terminals for voltage reading.

If you see higher than 16volts at battery then shut off engine, alternator/voltage regulator is bad, regardless of previous test at parts store

 

I tested the output while running. At the batt I got 12.11 and the alt showed 28

 

Test with engine off
Reads like Alternator is running wild, AC voltage, and B+ fusible link is blown, test B+ for 12volts with engine OFF

 

Batt reads 12.4 and rising, on the alt yellow black reads 12.42, green red reads 0, white black (on the 3 wire clip) reads 0, white black (single wire clip) reads 0, wire on 10mm bolt reads 0. Motor off readings

 

B+ fusible link is blown(10mm nut wire)

You will need Ford 12gauge fusible link, any autoparts store will have that.

It should come with Crimp-on ends attached, if not you will need two of those to splice ends of wires together.

Disconnect battery cables!!!!!! FIRST!!!!

Follow the Black/orange wire(B+), you will probably need to remove some of the wiring harness covering to do that
You will find the "blown" Fusible link towards the end where it connects to battery wire.
You will cut and strip end of Black/orange wire and crimp new fusible link to it
You will find the other "blown" end of old fusible link and cut and strip it's Red wire to attach other end of new fusible link

Tape any bare metal/wire parts of splices

reconnect battery, and test for 12volts at B+ 10mm wire again, if OK then start engine, if not a splice is no good, check it
Test battery voltage, should now be 14.6-14.9volts, if it is shut off engine and put Black/orange wire back in the harness as it was and tape it up
If voltage is higher than 16volts at battery then shut off engine and pull out alternator for retest at a shop.

 

Well ron you were right. It was my fusible link. However it wasn't bad.... It wasn't hooked up! I found it about an inch from its post. Now it's hooked up and I have charge! Thanks

 

Good work

Thanks for posting the fix