Is my alternator or battery(s) bad?

[purplehaiz]

i know im new but i need serious help. i have 2 dc lvl 4 xl 15s in a 91 mazda navajo. powered by an ma audio 4000. 3 extra intimidator batteries are in the back all linked by 0 guage wire. its all running on a stock 95 amp alternator. i normally idled anywhere from 14.0 to 15.0 on my volt meter. recently, my voltage has dropped and i idle at 11.5. sometimes ill see a slow increase to anything as high as 13.0. when the bass hits hard it now drops as low as 8.8. what i need to know is if my alternator is done or one of my batteries is done and is trying to compensate by taking power from another. i have a mechman 250 amp alternator that might be put on if it is needed. i just need to know what im in for. nobody can give me a straight answer. any help is greatly appreciated. i didnt know who else to ask.

[SnowDrifter]

Welcome to the forum!

Do you have a clamp meter? See how much power you are putting out from the alt if you can

I would bet your batteries are drained. That amp on the stock alt - the batteries are going to get discharged. Turn the car off, let it sit for an hour or so, then measure the voltage with a DMM and post back.

Do you have a battery charger?

Welcome to the forum!

[yUmadBro]

dropping to 8 volts is crazy low. change the alt

[purplehaiz]

im taking it to a local company to test my alt. if its not putting out what it needs to then the 250a will be in. with custom brackets and such. now. would it be easiers to swap the new one in or run duals. i would run the new one in place of the ac compressor. also. with the plug for the stock alt, 3 wires come out. but the plug on the mechman only has 2 that come out of it. what do i do.

[SnowDrifter]

dropping to 8 volts is crazy low. change the alt

I didn't drop that low car off on the stock battery running more power than him.

My money is on the batteries being discharged or loose connection.

purplehaiz: Have you done the 'big 3'?

I'm not sure how much power that amp draws / puts out. But I can guarantee it is more than the stock alt can handle.

[purplehaiz]

no actually if i swap the alt im just gonna gt the big 3 out of the way

[purplehaiz]

and that amp is a power hog from what ive read

[Riley Evan Houser]

How often do you start the car and how often are you checking the testing voltage with the car off? it could possibly be that one battery is shit and it's draining the other 2 to keep itself charged

[purplehaiz]

I start it pretty often. It's been staying around 11.7. But before when the voltage was fine the lights would kinda flutter real fast from dim to normal. Not that noticeably. Leading me to believe the batteries are draining due to the alternator. And I hammered that shit constantly.

[Guest]

those batteries are barely getting charged by that stock alt. if you have an agm battery charger, throw it on your batts overnight and that might help.