Hello this is my first post and im a bit frustrated lol. Ive got a new battery and alternator installed and my battery light wont go out and im losing charge. It seems the power is good until it exits the under hood fuse box. The fuse is good but the yellow/white wire that goes back to the alternator doesnt have proper voltage. I hope this is a good explanation of my issues and any feed back would be greatly appreciated. Thanks

 

Welcome to the forum

15amp fuse, #17 maybe, in engine fuse box is for the Yellow/white stripe wire.

12volts = Battery Voltage engine off, so measure battery voltage first, if it is 12.5v then thats "12volts" below, if it is 12.8v then thats "12volts" below
So when you measure voltage it should show "Battery Voltage"
Also test voltage with 2 different Grounds, use engine ground and then Battery Negative, to see if there is a difference, there should not be

Key off
Black/orange wire on the back of alternator(the bigger wire) should have 12volts, from Fusible link
Unplug 3 wire connector
Yellow/white wire should also have 12volts, from 15amp fuse, if it has less than 12volts but not 0 volts then wire is corroded or frayed at one end
Light Green/red wire should have 0 volts(this is the Battery Light wire)

Key on
Light Green/red wire should now have 12volts, this is the ON/OFF switch for the alternator, also Battery Light Ground when alternator is OFF.

An alternator can not just generate power by spinning it
It must have "startup voltage" to start generating power, thats what the Light green wire is for
Once alternator starts to make its own power, 13.5-14.9 volts, then Light green wire is no longer a Ground so Battery Light goes off.

If you give an alternator 12volts all the time then it will try to turn the engine when key and engine is off, so it would drain the battery

 

fingered it out. Thanks a bunch