Back to the Basics. What Alternator wire goes where?!

Ok guys. I have a 96 Ranger which I swapped a 97 5.0L powertrain into...started around two years ago. It is basically done now, complete with another transmission swap, delays, blah blah, you all know how it goes with projects

So I have forget how things were supposed to go. I am not even sure if harness is from the Ranger or Explorer. SVT says it shouldn't matter.

My alternator is not working, my brand new one isn't either. So obviously it is not wired up right, I believe it is not getting activated. I am confused and I think I will end up building my own harness from scratch, so lets go back to the basics. Here is a picture of the alternator:



Ok so the stud is where the power comes out (correct? Please tell me I at least got that right) so that goes back to the battery (or the top of the starter solenoid)

The whole case is grounded correct? It gets bolted to the block which should also be grounded to the frame (battery negative, block, and frame should all be connected right?

Ok and then there is the plug. There appears to be three conductors but the harness I have on there now (which may be wrong keep in mind) on has a plug with two wires coming out of it. Is one of those conductors not needed?

Right now I have a spare plug that has two wires going into it and one of the wires has a diode on it...whats that all about??! There are other wires in the current harness but I think they had to do with a remote starter and whatnot.

If I were making my own harness how would it go? Thank you all!

is this right?

I just bought a 1 wire alternator. alternator to battery. done lol

faststang90 said:

is this right?

Click to expand...

Right on. I can try that setup. I didn't know there was a mega fuse? Also the ignition switch wire...is that like a 12V switched? (only 12v when the ignition is turned on?)

Yes, the "I" wire usually comes from the Battery Light/voltage meter circuit, it is the ON/OFF switch for the alternator.
Usually the Light Green wire on the 3 wire connector.

An alternator is an electric motor used in reverse, if left ON it would drain the battery trying to turn the engine, lol.

When you turn on the key the voltmeter/battery light circuit gets 12volts, the "I" on the alternator "acts" as a Ground since alternator is not turning(producing voltage) so with 12volts on one side and "ground" on the other side the Battery Light Bulb comes on.
When you start the engine the alternator starts producing voltage so the Battery light now has 12volts on one side and 12volts on the other, so Bulb goes out/off.
This 12volts also powers voltage regulator circuit which powers the alternator so without the 12volts at "I" alternator is OFF, so it won't drain any power via the big B+ wire(large stud)

AH that makes sense. So...my harness has two wires and the alternator had three studs. Is the S optional?

Also my battery light was never on even though my battery was draining...but my voltmeter was reading the voltage of the battery...is that a separate circuit? Must be eh?

Well there is battery voltage and "running voltage"
With engine off Vehicle batteries have 12.8v new, 12.2v after 5-6 years and due for replacement.

Running voltage should be 13.5v, approximately 1volt above battery voltage with engine off.
First start voltage will be above 14.5volts then slowly drop down to 13.5v, 2 to 5 minutes, that's "recharge voltage", battery needs a big hit of voltage after starting engine.

So voltmeter should go up a bit when engine starts.

"A" and "I" are used on the 5.0l engine harness, "S" is not.
Light Green wire for "I"
Yellow for "A", it runs to a mini fuse in power box, fuse #6 in my '97 explorer diagram

RonD said:

Well there is battery voltage and "running voltage"
With engine off Vehicle batteries have 12.8v new, 12.2v after 5-6 years and due for replacement.

Running voltage should be 13.5v, approximately 1volt above battery voltage with engine off.
First start voltage will be above 14.5volts then slowly drop down to 13.5v, 2 to 5 minutes, that's "recharge voltage", battery needs a big hit of voltage after starting engine.

So voltmeter should go up a bit when engine starts.

"A" and "I" are used on the 5.0l engine harness, "S" is not.
Light Green wire for "I"
Yellow for "A", it runs to a mini fuse in power box, fuse #6 in my '97 explorer diagram

Click to expand...

So there should be a plug coming out of the power box? I have looked forever and I can't find it. Does one of those lines have a diode in it? I am leaning toward just taking out my alternator harness and making my own anyways. As I am typing this I just realized I didn't swap my fuse box...I still have the fuse box from my 96 ranger in there. That may be why i can't find the plug eh. But the ranger fuse box should have the same provisions for the ranger alternator I guess. I'll just have to find out where that is and tap into it for the explorer alternator?

Ford went back and forth using fuses(in fuse box) some years and fusible links(on the wire) in other years.

The '96 should use a fusible link for Black/orange wire(B+) it would be located on the power block(post) on starter relay, fusible link is a shorter wire that would connect power block(battery) to Black/orange wire, this wire is a smaller gauge than the black/orange wire and made of materials that will melt and separate(blow) without sparking or starting a fire.
Fusible links are used because they will not blow instantly if there is a power spike, they are an inexpensive version of a "Slow Blow" fuse.

Then there are 2 fuses for the '96 charging circuit
In engine fuse box Fuse #17 15amp is for the yellow/white wire on alternator
In the cab fuse box Fuse #15 15amp is for the charge indicator(battery light) and powers the Light Green/red wire at alternator.
This #15 fuse is between ignition switch and battery light, so if battery light is working then that part of the circuit should be OK.

On mine (completely different truck I know) I noticed two pins in the connector were reversed on my Ranger's connector vs the Explorer one I clipped off at the JY when I got an alternator. When I put the Ex alternator in I swapped the connectors so it would still line up with how the Explorer harness was. So far (3.5 years) it works great.

Ranger had been converted to internal regulated and took an alternator for an '86. I know Ford used that big clunky looking style alternator for quite awhile, maybe it lasted until your '96 and beyond.

I have pics here if you haven't found on your own.

http://www.therangerstation.com/forums/showthread.php?t=133205&highlight=fead

RonD said:

Ford went back and forth using fuses(in fuse box) some years and fusible links(on the wire) in other years.

The '96 should use a fusible link for Black/orange wire(B+) it would be located on the power block(post) on starter relay, fusible link is a shorter wire that would connect power block(battery) to Black/orange wire, this wire is a smaller gauge than the black/orange wire and made of materials that will melt and separate(blow) without sparking or starting a fire.
Fusible links are used because they will not blow instantly if there is a power spike, they are an inexpensive version of a "Slow Blow" fuse.

Then there are 2 fuses for the '96 charging circuit
In engine fuse box Fuse #17 15amp is for the yellow/white wire on alternator
In the cab fuse box Fuse #15 15amp is for the charge indicator(battery light) and powers the Light Green/red wire at alternator.
This #15 fuse is between ignition switch and battery light, so if battery light is working then that part of the circuit should be OK.

Click to expand...

I will have to check those fuses as I cannot quite remember if the battery light is on (the truck is currently 175kms away...so I only get to look at it the odd time unfortunately)

85_Ranger4x4 said:

On mine (completely different truck I know) I noticed two pins in the connector were reversed on my Ranger's connector vs the Explorer one I clipped off at the JY when I got an alternator. When I put the Ex alternator in I swapped the connectors so it would still line up with how the Explorer harness was. So far (3.5 years) it works great.

Ranger had been converted to internal regulated and took an alternator for an '86. I know Ford used that big clunky looking style alternator for quite awhile, maybe it lasted until your '96 and beyond.

I have pics here if you haven't found on your own.

http://www.therangerstation.com/forums/showthread.php?t=133205&highlight=fead

Click to expand...

I think mine may be switched too actually... I will have to check

So in conclusion...the yellow wire is 12v all the time and the green/red wire is 12v when the ignition is turned on? And the yellow is on the ...left side? (if the flat part of the half moon connector is down?) I can't quite tell from that picture. Then the green/red wire is on the right side? And the middle pin aint used?

Dweano said:

I think mine may be switched too actually... I will have to check

So in conclusion...the yellow wire is 12v all the time and the green/red wire is 12v when the ignition is turned on? And the yellow is on the ...left side? (if the flat part of the half moon connector is down?) I can't quite tell from that picture. Then the green/red wire is on the right side? And the middle pin aint used?

Click to expand...

Calling the locking tab up, my yellow wire is to the right and the green wire is to the left. Yes, green is hot with key and yellow with battery.

85_Ranger4x4 said:

Calling the locking tab up, my yellow wire is to the right and the green wire is to the left. Yes, green is hot with key and yellow with battery.

Click to expand...

Alright, all is clear now. I will check it out this weekend and see what I can see with the multimeter. Thanks for your help!

Hmm, well the fuses mentioned by RonD are both good. The plug is wired correctly. The yellow wire gets battery voltage (almost) all the time, but the green and red wire gets 0.00v while the truck is running. So I think I found my problem. Which would also explain why I can't remember seeing the battery light...dangit. So if it isn't the fuse is there anything else I could look for? I followed it back to the plug by the ABS module and then it disappears into electrical land

If only the fuse was blown! Haha

Edit...or if it is just a switched 12 could I do a redneck fix for it off of some other 12v switched source?

Yes, the green wire is the ON/OFF switch for voltage regulator/alternator.

For 1996 Ranger, check Fuse #15 in the cab fuse box, 15amp, that powers the battery light alternator circuit, this circuit didn't used to have it's own fuse, not sure when they added it, it used to get power from main ignition switch fuse in engine fuse box, and if that blew truck wouldn't start