No power to alternator green/red wire on dash light

The large fat wire is the battery wire and the other is the field wire or regilator feed wire from the ignition light.
This may help;
https://forum.ih8mud.com/threads/cs-144-wiring-help.598784/

most alternators are just 2 wires yellow/green usually go to the dash bulb to say alternator is working, thick red is direct to battery, some models have an extra earth, there are a few types of duel alternators that are designed to charge more than one battery, these have 2 bolt polls one standard size and another half the size this one is for the spare battery i.e battery for fridge etc. hope this helps. battery light on dash is usually spade connector.

Burnt fuse or fusible link, maybe . Check for B+ voltage on the heavier gage wire on the back of the alternator , Does the charging light on the dash lite ? Besides the heavier wire on the back ,how many others are hooked to the alternator ? Two in a connector ? Is one red ? this also should have B+ voltage . The last one , brown ? With the key on an the charge light lit on the dash this wire should have power also.

You can't ground a power wire. If you have the schematics, look and see were the power comes from. Could be a fuse or from the ignition switch. If everything else works, I run a new wire, instead of opening up the harness to find the short.

This light on dash is telling you, alternator is not charging or current is not reaching battery. With a voltmeter check your alternator output at battery. It should be at least 13.5 volts. If less than that check output at back of alternator, big red wire bolted to alternator. If voltage is within specs. then you may either have a blown fuse, open(broken) big red wire from alternator to baterry. Check big red wire circuit integrity by proving back of alternator where wire bolts to alternator. With the engine not running, there should be battery voltage at that bolt/wire. If no voltage repair open in circuit, either a fuse or broken wire( usually). If still no output(13.5 volts) or more, check power ground to alternator plug. If these power ground check out ok, then you more than likely have a defective alternator.

green/red is the charge lamp circuit. when grounded it should turn the light on,if it doesnt, you may have a blown fuse. the lamp circuit provides the "turn on" signal to the alternator as a positive voltage. the voltage regulator is a gounded load until the alt starts charging, than it puts out a positive voltage to turn out the light.

The gray-yellow wire from the key switch powers the charge light.
The light green-red wire goes from the charge light to the alternator.

at alternator gig wire battery voltage,one wire battery volts one less . battery volts wire goes to automatic shut down relay, less then battery voltage wire to pcm fuse will be 20 amp just ck all that size.

check the black/orange wire at the alternator for battery voltage if no power check the fuesable link ( A )

check the orange/light blue wire at the alternator for battery voltage if no power check the fuesable links ( B & C )

check the light green/red wire for 12 volt with the engine running if no power replace the PCM.

if all wires have the proper voltage then replace the alternator

GOOD LUCK

Check the big red wire on the back of the alternator for power. The wire likes to get corroded in half inside the casing but is still held together BY the casing. you can even take a jumper cable from the positive side of the battery to the big/single wire on the back of the alternator. Now , you could have a bad ground also. take a voltmeter or test light and with the ground of the tester on the ground of the battery check for power on the case of the alternator. Another thing , does the alternator or charge light on the dash light up woth the key off? the alternator knows to "start-up" or "field-up" by the power it recieves through the bulb before the engine is started. once the engine starts the small brown wire on the alternator goes hot and shuts the light on the dash off cause it now has power on both legs of it. if the bulb blows then the alternator won't field-up. good luck. Scott