I've changed my alternator because my old one barely charged my battery and now whenever I turn off the car I get a buzzer and my battery light comes on while the keys are out the ignition. I found out that it comes from my wire from the back of my alternator to the positive battery terminal. Do I need that wire connected or is there a way to fix it.

 

That would indicate the alternator you installed is faulty. Yes you do need that wire.

No one makes a good CS130 anymore due to parts to build quality units not being produced anymore.

DC Power Engineering and Mechman both make CS130 replacements that are much better than the originals.

https://www.dcpowerinc.com/

https://www.mechman.com/

GD

 

Usually the way a charging indicator light works is the power source is in the gauge panel, and the light is grounded through the alternator. The bulb lights up with key on and alternator not charging. Once the alternator begins charging the voltage is balanced across light bulb (both sides at system voltage) and the bulb turns off.

If the light bulb is on with key off then it means there is still power to the gauge panel.

 

I should be good if I hook it up to a switch then.

 

QUOTEi just put another alternator on after the other new one wasn't charging, this one will charge at idle but when I get driving it'll drop to 10 volts. I'm not sure what the problem is, I checked my fuses and I wired my fan to a switch.

 

Aftermarket alternators are $hit. As you are seeing. If it was working but "barely charging" before you switched the alternator and now it has yet a different problem - very much suspect the alternator is junk. Where are you buying them?

GD

 

I tested it and it's putting out 12 volts so I'm thinking it's my gauge, I'm just gonna cap my idiot light and install some new gauges.

 

It needs to be putting out 14.5 volts. 12v is not charging. A fully charged battery is 12.6v.

​​​​​​The idiot light is telling you it's bad. "Capping" it - what ever that is - is ignorant and foolish.

GD