Battery light on after new battery

[ryan2.3]

I have a company car so i haven't been using the mazda much these days and i keep it stored at work at one of the parking garages. I try to get out there once a week, take it out for lunch, give it a car wash then park it. However, i haven't been able to in about a month.

last week i went to try it and it was dead, hooked up the truck to boost it and it started up right away, looked up and noticed the overhead lights were on... stupid me.

however, as soon as i unhooked the jumper cables, the car immediately died. Didn't matter how long i let it sit, it'd just die as soon as it disconnected.
Fast forward to today, picked up a 24F battery from Costco ($83 after tax wooo) and while the car started up instantly and allowed me to drive it home the battery light stayed on the whole time. It was only about a 20 minute drive (about 12 miles) and i got a carwash along the way too.

I'm worried it's likely alternator (i hope my Gen 2 alternator that hasn't sold yet will fit) but i wanted to know if its possible this could be due to sitting dead for a month and after some more driving/mileage it'll go away on it's own. Like something needs to relearn

if thats not the case, guess i know what i'm replacing this afternoon

[ryan2.3]

One more thing to add. My dash lights/headlights don't change regardless of what the headlight stalk is turned too.
It stays bright red (it won't dim and bring up the blue back lighting)

[FD22]

If it's alternator, you should start getting the symptoms I was getting before we replaced mine. At least you've done it before now

[morganc]

The battery light is solely there to indicate that "there's a net discharge in the system" meaning faulty alternator. Going forth, I'd recommend making a point of taking your mazda out for a drive 20 minute drive weekly to keep everything in good working order

[Noisy Crow]

One more thing to add. My dash lights/headlights don't change regardless of what the headlight stalk is turned too.
It stays bright red (it won't dim and bring up the blue back lighting)

Check headlight fuse. Other than that...stuck relay? I'd have to dig out the wiring diagram, haven't looked at the headlight wiring schematic in ages.

[ryan2.3]

If it's alternator, you should start getting the symptoms I was getting before we replaced mine. At least you've done it before now

I hope the gen2 is the same or at least maybe it's the voltage regulator and I can swap that.

The battery light is solely there to indicate that "there's a net discharge in the system" meaning faulty alternator. Going forth, I'd recommend making a point of taking your mazda out for a drive 20 minute drive weekly to keep everything in good working order

Yeah i was doing that. Then things got busy and I kept telling myself "tomorrow".

Check headlight fuse. Other than that...stuck relay? I'd have to dig out the wiring diagram, haven't looked at the headlight wiring schematic in ages.

I'll have to look at that. Relay I can see but fuse, wouldn't they stay off if it blew?

[Noisy Crow]

I'll have to look at that. Relay I can see but fuse, wouldn't they stay off if it blew?

The way you wrote the post, I was thinking the lights are not coming on.... the dash dims etc. when the headlights are turned on.

[ryan2.3]

The way you wrote the post, I was thinking the lights are not coming on.... the dash dims etc. when the headlights are turned on.

yeah it was weird, there were lights on (can see the reflection in the car infront of me, but the dash lights weren't changing with turns of the stalk. I left it at work the last couple days, since i have tomorrow off i'll bring it home to spend the day. need to also do brakes, cabin filter and now possibly alternator

[ryan2.3]

Pulled 2 alternators from the scrap yard and the first one I tried worked fine. Took a few drives today. Lights seem to be fine as well however I've got 2 new codes I'm not familiar with. P2004 and p2503. Based on what they mean I don't think they're related but it'd be an odd coincidence to just appear here as this issue was happening