alternator won’t charge battery.
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From: Fort Collins,co
alternator won’t charge battery.
Alternator won’t charge battery, battery light won’t come on. Narrowed it down to the 3 wire plug(LG RED, purple jumper, SM grey). LG red is always hot(showing battery voltage), grey should be hot with the ignition in the on position(engine off) but no power. Hot tapped grey wire and alternator started putting out 15v with engine running. Checked fuse for instrument cluster and it checked out. All warning lights work besides battery light. Please help!!
Welcome to the forum
Ford changed the charging systems on Rangers 4 or 5 times, from 1983 to 2012 so what YEAR is your Ranger and what engine?
Always include these in all questions
From wire colors I will GUESS 2006 to 2012
In 2004 Ford change to a digital dash and charging system, microprocessor control, gauges still "look" analog but they are digital
Google: ford HEC mode
The Grey wire, used to be the light green wire, it provides the alternator its Start Up voltage, and is also the Battery Light Circuit.
An alternator can not START to generate voltage unless it HAS voltage to start with, and if you give an alternator voltage all the time it will drain the battery, so it needs Key on voltage
Yes, the B+ and Voltage regulator, both red wires in 2006, should have 12volts all the time, they are not the Rotor, just the Fields so can't drain battery.
The Grey wire should show 12v key on and battery light should be on when grey wire connected to alternator/regulator.
You said you checked the battery light fuse, in 2007 that's fuse #9, 5amp, in Smart Junction Box(cab fuse box)
If fuse is OK then the Grey wire is broken in the engine bay, follow it from alternator back, may have to pull off its wire loom covering
The grey wire is the GROUND for the battery light bulb, so if Battery light is not coming on(and bulb is OK) and fuse is OK then grey wire is broken, for sure
The voltage regulator is a GROUND until alternator starts to generate voltage, which is why battery light comes on with the key, and then goes off when alternator is working, if alternator stops generating voltage then battery light comes back on.
Giving Grey wire 12v should cause alternator to start generating voltage if thats the problem, so it is the problem, find that broken wire, I doubt it would be in the cab, but..............
Ford changed the charging systems on Rangers 4 or 5 times, from 1983 to 2012 so what YEAR is your Ranger and what engine?
Always include these in all questions
From wire colors I will GUESS 2006 to 2012
In 2004 Ford change to a digital dash and charging system, microprocessor control, gauges still "look" analog but they are digital
Google: ford HEC mode
The Grey wire, used to be the light green wire, it provides the alternator its Start Up voltage, and is also the Battery Light Circuit.
An alternator can not START to generate voltage unless it HAS voltage to start with, and if you give an alternator voltage all the time it will drain the battery, so it needs Key on voltage
Yes, the B+ and Voltage regulator, both red wires in 2006, should have 12volts all the time, they are not the Rotor, just the Fields so can't drain battery.
The Grey wire should show 12v key on and battery light should be on when grey wire connected to alternator/regulator.
You said you checked the battery light fuse, in 2007 that's fuse #9, 5amp, in Smart Junction Box(cab fuse box)
If fuse is OK then the Grey wire is broken in the engine bay, follow it from alternator back, may have to pull off its wire loom covering
The grey wire is the GROUND for the battery light bulb, so if Battery light is not coming on(and bulb is OK) and fuse is OK then grey wire is broken, for sure
The voltage regulator is a GROUND until alternator starts to generate voltage, which is why battery light comes on with the key, and then goes off when alternator is working, if alternator stops generating voltage then battery light comes back on.
Giving Grey wire 12v should cause alternator to start generating voltage if thats the problem, so it is the problem, find that broken wire, I doubt it would be in the cab, but..............
Last edited by RonD; Oct 23, 2018 at 10:18 PM.
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