alternator

adrian p

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afternoon everyone. my alternator was checked by autozone and pepboys. both said it was good but i only have battery voltage at the battery.any helkp would be appreciated.
 

Tiha

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What year is that? Does it have an external regulator? Little square box on the fenderwell?
 
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adrian p

adrian p

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Tiha thanks for the response. its an 87 but i believe it has a 97 explorer 4.0 in it so im not sure about the external regulator
 

Tiha

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Does your battery indicator light in the dash work?

87 or 97 will both be internally regulated. So no problem there.
 

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L\Bronco

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Hey Adrian, if you are running the 97 explorer alt still it will definitely be an internal regulator. it should look like this(ish).
alt.jpg
If you look at the 2 screws on the back of the regulator that hold the brushes in place inside, there is usually an arrow on the plastic body of the regulator pointing at one of them with text that reads "ground here to test" If you ground that ***** with the engine on the alternator should go to max output (full field). You may have to pry off a plastic cap.
Caution, If you ground the wrong ****** you might burn a fuse!

The alternator should have 4 wires on it, a big Blk\og one bolted to the main terminal, and a yel\wht, wht\blk, and a Light green\R in a 3 terminal connector plugged into the regulator.
The big one (black with an orange stripe should be 12v at all times. It is fed by 2 fuse links at the starter relay near the battery.
The Yellow with a white stripe is 12V at all times from fuse 6 in the under hood fuse box. (In the explorer harness)
The white\black is stator power and loops from the three wire plug, back into the alternator on a single plug.
The light green\red comes from the ground side of the alternator light in your instrument cluster and should have 12v with the key on and the harness unplugged from the alternator. (It has to be fed through the bulb in the cluster or a resistor. This is the circuit that excites the regulator to start the charge.)
I'd focus on main power and the Y\W and Lg\R wires to start, especially the Lg\R one.
I'm not sure what harness is in yours, but this is what your alternator needs to work. The power supplies can come from different places so you may have to hunt a bit.
(This is the fun part of a resto mod!)
That should give you enough to get going.
Cheers
 
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L\Bronco

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My pleasure!
Heres the diagram for the explorer bit, to add to the one Tiha put in (you will need to use both. (its been my life lately mixing 03 Navigator with 79 Bronco)explorer harness.jpg

Cheers
 
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adrian p

adrian p

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L\Bronco thanks for the info.found a burnt in half wire on the blk/og wire at the back of the alternator and the alternator is putting out power now. Now to the next issue wire was super hot(obviously reason for the wire connector melting) so i decided to check the voltage on the same wire while running and im at 15.5 volts. So does that mean the regulator on the alternator is bad and not regulating within the proper voltage? the vo;tage at the battery is 13.5 volts while running
 
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L\Bronco

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L\Bronco thanks for the info.found a burnt in half wire on the blk/og wire at the back of the alternator and the alternator is putting out power now. Now to the next issue wire was super hot(obviously reason for the wire connector melting) so i decided to check the voltage on the same wire while running and im at 15.5 volts. So does that mean the regulator on the alternator is bad and not regulating within the proper voltage? the vo;tage at the battery is 13.5 volts while running
That means you are losing 2v in the Blk\Og wire somewhere due to high resistance. I'd fix the resistance first. 15.5V isn't crazy high if the alt is not hot (The charging voltage goes up and down with temp from 13.2ish to 15.5ish. Its not that long of a wire, so test the voltage at a few spots along the way from the alt to the batt. You are looking for the spot that it changes from 15.5 to 13.5V. It will likely show as a temp change too, from cool to warm. Do you have access to a thermal camera? ( you may have to compromise the insulation a bit to check the voltage, but you will likely be replacing some wire when you find the culprit.) The thermal camera is remarkably fast and easy if you have access to one. Make sure any new wire is at least as large or larger than the factory black\orange.
Then see what the voltage does once the alt and battery are within .5 of each other. (That's the limit)
Happy hunting!
Cheers
 
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adrian p

adrian p

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L\Bronco followed the og/blk wire and ended at a 30 amp fuse in the cab.ohms readings were good.went ahead and did what is frowned on and disconnected the battery ground while running(thinking it would tell me if the battery was drawing too many amps due to being weak) still read 15.5 volts at the alternator.im thinking the voltage regulator in the alternator is bad.confirm or deny?
 

Tiha

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Yeah I would agree alt is bad.

Parts stores test them for free, but we say anything over 14.5 volts is bad.
 

L\Bronco

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L\Bronco followed the og/blk wire and ended at a 30 amp fuse in the cab.ohms readings were good.went ahead and did what is frowned on and disconnected the battery ground while running(thinking it would tell me if the battery was drawing too many amps due to being weak) still read 15.5 volts at the alternator.im thinking the voltage regulator in the alternator is bad.confirm or deny?
Sorry Adrian, are you talking about the big wire from the alt. ? It should go to a fusible link at the solenoid. Also I wouldnt use an ohm meter on the wire. Leave it charging(running) and check the voltage on the wire from the alt to the solenoid in a few places along the way. (you will have to do what is also frowned upon and poke through the insulation)
If you can find the spot where it drops from 15.5 to 13.5, it will be ypur bad connection.
I agree 15.5v is a bit high, but if the wire the alternator uses as the sense line is from the battery, it will explain the high number.
I wouldn't focus on the alternator until the wire that carries the current is verified first.
Hope that helps
Cheers
 
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adrian p

adrian p

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this wiring is a shit show.forget everything i said a about it going to the fuse box in the cabin.started ringing it out.,cutting electricle tape and what not.this is a can of worms i just opened.first photo is where two conductor wire should have the frangible fuses but goes into a cylindrical solid connector and those wires have frangible fuses.the second pic should be a starter solenoid but is now a terminal block. the third pid is where the blk/og wire is connected straight to the battery. for those that read all this thank you and for those that can make sense of this madness thank you more.i see alot of wiring in my future.
 

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