Alternator

Grossfade · Aug 28, 2016

i have a 97 ranger 4.0 5spd 4x4, regular cab no power window/lock

the alternator was not working when i got it, the wiring harness was cut and spliced, replaced it all, from alt to solenoid, and even to the starter, brand new alternator, no blown fuses that i can find to test, getting power to the main feed to the alt(black/orange wire bolted to the back of the alt to the solenoid

the 3 wire plug is in good condition, small plug with the white/black wire is good, the yellow wire is hot.. the green wire however is not hot, if you jump fire from the yellow wire to the green wire at the plug, with the truck running, the alternator starts charging as it should, everything works... shut the truck off and start it back again, it may charge and it may not, jump the yellow to green wire again, and it charges however the green wire, still has no fire even when the alt is charging

checked the grey/yellow wire coming from the ignition switch, it is hot.. not sure if that is the correct wire to check

any suggestions? bad ignition switch? bad instrument panel, any fuse i have over looked, why does this green wire get no fire

RonD · Aug 28, 2016

The Green wire on the 3 plug connector comes from the Battery Light in the Dash.

This wire is used to turn ON the alternator, this is why alternator starts to work when you "jumped" 12volts to the green wire.

An alternator generates power by applying power to the Rotor, 7 to 9 volts, the spinning of the rotor causes the 3 fields in the alternator case to generate AC Volts, which is converted to DC volts(13.5 to 15volts) and sent out on the B+ post to the battery/vehicle.

Once it is spinning an alternator runs on its own internally generated power, that power goes to the ROTOR to make more power but.........................BIG BUT
To start to generate power it NEEDS power to the ROTOR first, that is what the Green wire provides.

1998 ranger uses fuse #15 in the cab fuse panel, 7.5amp, to power the Battery Light/Green wire.
Same setup in 1999 but not sure of the fuse number.

How the Battery Light works is fairly simple.
When you turn on the key fuse #15 sends 12volts to battery light bulb, which passes thru the bulb and to the alternator(green wire).
When the engine is off the alternator is a Ground, so with 12volts on one leg and a Ground on the other leg the bulb lights up, Battery Light on.
When engine starts the alternator is now generating power, assuming it is, then there is now 12volts on one leg of the bulb and 12volts on the other leg of the bulb, so bulb is OFF

Grossfade · Aug 29, 2016

so, basically what your saying is, since i have power to the 7.5amp fuse, which is number 15 in my fusebox, and it is not blown, but i have no power to my green wire, then it must be between the fusebox and the alternator plug, and it runs through the battery light in the dash, which does not work, and that is my problem?

seems odd to me..., but i understand what you are saying, just seems strange that a warning light in the dash could cause your truck to stop charging, insane lol

when i turn the key on, and crank the truck, no alernator light ever comes on, though i admit i do not know where the light is, the volt gauge does work however, just no warning light even when the alt is not working

if i pull the dash out, which bulb will it be, is it replaceable?

Grossfade · Aug 29, 2016

ok, i pulled the dash out, bulb looks fine, however i noticed when you crank the truck, half of the brake light lights up for a second then goes away, no other lights

and i discovered, crank the truck, not charging.. unplug the bottom white plug from the back of the instrument cluster, it starts charging, shut it off and crank it back,not charging.. plug it in, not charging.. unplug it and it starts charging

i noticed corrosion on the copper connections.. i am hoping if i replace the dash my problem will be solved

picture of the plug and corrosion http://i.imgur.com/OIzQp4G.jpg

RonD · Aug 29, 2016

That picture shows the back of the Battery Light Bulb, BATT

And that resistor is part of that circuit, if bulb should fail 12volts would still go out that Green wire to the alternator thru that resistor, it is a backup circuit in case bulb burns out.

"....just seems strange that a warning light in the dash could cause your truck to stop charging", that resistor prevents that from happening, but in this case the connection is the issue not the bulb, you may be able to clean it up connections and get it working again

Grossfade · Sep 1, 2016

it seems that connection was indeed the issue, i replaced the dash, and now everything works as it should

i discovered that my windshield is leaking, and it drips right ontop of the steering column, and wets the dash.. i believe this caused the issue, i sealed the top of the windshield, hopefully it will last until i can have it replaced

now! my only issue is the fact that all my dash lights were originally blue, now my gauges are green, is there any way to change the color? i took apart my old dash and discovered that the plastic pieces with the numbers printed on it, have a blue tint, bulbs are clear.. and i assume changing the color of the bulbs in my new dash will not change the color?

RonD · Sep 2, 2016

Leaking windshield will be from rusted out lower corner on either side, not a Ford issue just general vehicle issue.

Water can get in anywhere around the outside edge of the window, behind the trim, it then travels down the outside edge of window and sits in the trough at the lower corners.
Over the years it can rust through and then it will leak in to the cab

You can remove trim and seal around outside edges then put trim back on but it will still leak over time.

Windshield can be removed and the rusted out areas fixed then windshield is reinstalled.

Alternator

Grossfade

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