Hey guys (and gals). I could really use some suggestions regarding an issue I'm having with loss of power and my battery light coming on.

I just replaced the alternator yesterday night, and when i went to drive the truck, the battery light still came on and my gauge was reading really low. I also made sure to charge the battery up prior to driving it after the ALT swap.

Typically, this issue is a "no-brainer" with ANY vehicle, and replacing the ALT solves the problem, but not in this case. This truck is my everyday driver and I need it to get to work, so ANY AND ALL help, tips, and/ or suggestions will be greatfully recieved. Thank you so much, in advance.

 

Welcome to the forum

You need a volt meter to test the system, reason being is that there are 3 fusible links inside wiring harness that you need to test, and easiest way to do that is with a volt meter, or worst case a 12v Test Light

Alternator has 4 wires connected, only 3 really as one is just a loop wire

Key OFF
Test for battery voltage(12.3-12.8v) at B+ terminal on the back of alternator, the terminal with stud and nut, larger Black/orange stripe wire
This wire is connected to battery directly thru 2 fusible links.

Unplug the 3 wire connector
Test the Yellow/white stripe wire for battery voltage
This is connected directly to battery by one fusible link but thru one of the above fusible links, so if B+ had 0 volts this one will too

Check voltage on Light Green/red stripe wire, should be 0 volts
Turn key ON
Test that wire again, should now be Battery Voltage, this is the Battery Light circuit, which is also the ON/OFF switch for alternator.
Turn key OFF

If all voltages tested GOOD then plug connector back in, and make sure the Jumper White wire is correctly plugged into the 4th connection on the alternator, it can go in crooked and not make a good connection.

Start engine
Test voltage at battery, should be above 14volts, if it is not then new alternator is bad, period


A fusible link is like an in-line fuse, and a "slow blow" fuse in one package
It is a short wire spliced into a larger wire, if the AMPs get too high for too long then the fusible link melts and separates, breaking the connection, like a regular fuse does
But a fusible link won't burn like a regular wire will, i.e. black smoke, dripping melted plastic insulation and maybe a fire.
Fusible link insulation vaporizes and the metal wire separates without causing a fire

These will be located closer to fuse box end of alternator wiring, so if you have a problem then thats where you need to start unwrapping the wiring harness to find the Fusible links.
The two main fusible links will be hooked to larger Red wire coming out of the fuse box.
The Yellow wires fusible link will be attached to the other end of one of these main fusible links