Bad Alternator? Something else? High amp replacement? (1 Viewer)

[cbbr]

2000 LC 100. Dual batteries (27 Interstate & 31 Optima Yellow Top) with a RedArc BCDC1250D. The accessories (firdge/winch/offroad lights/EcoFlow house battery) all run off of the Optima. So the starter battery really is just a starter battery.

I had to slam on the brakes yesterday and the battery light cam on along with the ABS/Atrac lights. TorquePro showed voltage in the 8-9V range and it fluctuated from idle to running. I connected the starter battery to the Optima and back-flowed the EcoFlow to the Optima to make it home.

It had an older battery, so I put in a new Interstate. The voltage now is 11V (TorquePro) while running and at idle. No real fluctuation. The battery light is still on, all others are off. The dash gauge corresponds to the OBD reading. No OBD Codes.

So my questions are 1) Alternator or something else? 2) Assuming that it's the alternator, I would rather a higher amperage replacement, so what's out there that is proven in our trucks?

 

[GTV]

It does sound like the alternator, mine was acting similarly. I upgraded with a 180a from DC Power and upgraded the charge cable/fuse and engine grounds while I was at it.

 

[nissanh]

When did you last replace the brush kit inside the alternator?

What is the voltage at the battery when tested with a volt meter?

 

[cbbr]

the alternator appears to be original and shows 11V, so I ordered a new one. Just having 300K on it tells me that it is time. I read a bunch of threads here and ordered one of these. They are well reviewed and I can use the bump in amperage. I will post up after I get it installed either way.

 

[nissanh]

Looks like Made in USA and a reputed seller. Should be good and possibly a good source for A/M alternator.