Battery light in dash is on

[buliwyf]

This morning, when I started the car, the red battery light on the dash was constantly on.

My battery is just 6-months old.

Car started just fine, and I tried shutting the engine off and starting it again and it did so without any problems. I didn't drive it to work for fear of stalling in the middle of the road.

Could it be my alternator dying?

Or (hopefully) my battery is just crap and I just need to replace it? Although if my battery is weakened, I will be able to feel it when starting the car, right?

Could it be just a faulty sensor / connector / terminal?

 

[buliwyf]

Also to add, it was raining hard the day before, from work to home. Maybe something got wet? Or the belt was slipping? I didn't hear any squeal though. Plus, wouldn't it be dry by that time overnight?

 

[Preferio]

This morning, when I started the car, the red battery light on the dash was constantly on.

My battery is just 6-months old.

Car started just fine, and I tried shutting the engine off and starting it again and it did so without any problems. I didn't drive it to work for fear of stalling in the middle of the road.

Could it be my alternator dying?

Or (hopefully) my battery is just crap and I just need to replace it? Although if my battery is weakened, I will be able to feel it when starting the car, right?

Could it be just a faulty sensor / connector / terminal?

The ECM detects output voltage of the alternator, so it wouldn't simply be "a sensor" however, the IAT sensor is on the same circuit (don't ask why, because I don't know and personally think Mazda is retarded for having done that, though I suspect there is some reason behind it) and will cause the charge light to illuminate.

 

[pasadena_commut]

Careful - if the alternator belt breaks and falls off the first indication may be that battery light. Since the same belt also drives the water pump, this can cause the car to overheat very quickly. Eventually the battery will drain and the car will die, but that could be well after the car blows up the radiator, water pump, overflow tank, and potentially damages the motor. So before you do anything else, please make sure that the alternator belt is still there and that it is still turning all the bits that should be. (Visually, don't stick your hand in there with the car running!)

In my experience a lit battery light on a running car is usually alternator related. When the battery goes it tends to be that the car has more and more trouble starting, but the battery light is not on once it is running.

 

[The_big_dill]

Put a multimeter across the battery terminals, what does it read when the car is running?

 

[Fresco]

Put a multimeter across the battery terminals, what does it read when the car is running?

I have the same problem but mine comes on randomly, I have a cigarette lighter volt reader and it'll read from 14.2v-12.8v, and my torque app reads 12.8v constantly from the ob2 port, I had it load tested and the report said 13.8v across the board, so could i have a faulty iat sensor

 

[Nouse4aname]

Ours had this issue. Turned out to be that the ground for the alternator had corroded and wasn't even fully connected anymore which was causing the issue. Replaced that and the battery cable ends too. Now all is well.

 

[buliwyf]

What is this? Is this the IAT?

I tried disconnecting it, then reconnecting it. Now the CHECK ENGINE light is ON too, together with the Battery light!

I'm trying to look at the alternator but it is buried deep underneath the engine bay. I can't even get my skinny hands/forearm to reach the connectors. The alternator belt looks new-ish, it has still got those "dayco" painted labels and it looks newer than the other belt beside it.

 

[The_big_dill]

What is this? Is this the IAT?

I tried disconnecting it, then reconnecting it. Now the CHECK ENGINE light is ON too, together with the Battery light!

I'm trying to look at the alternator but it is buried deep underneath the engine bay. I can't even get my skinny hands/forearm to reach the connectors. The alternator belt looks new-ish, it has still got those "dayco" painted labels and it looks newer than the other belt beside it.

Well yeah your going to get an engine light if you unplug that sensor, the ECU doesn't know what the air temperature coming in when thats unplugged...

A corroded cable can be a cause to this, I have had that issue on my motorcycle, but that was built in 1987.

In any case, check what the battery voltage is at when car is on.

 

[buliwyf]

Multimeter reads 14.3v for about 10mins of idling. The battery light is now gone. Soon after, the check engine light is gone too.

What could've caused this?

 

[The_big_dill]

Could be anything. But don't get too excited, problem might come back

 

[Fresco]

I replaced my iat sensor this morning, just did a 60 mile road trip and happily the light did not come back on, it always came on after 20-25 miles of driving and now nothing, I'll keep an eye out for about a week and will report back

 

[Fresco]

Well that didn't last long lol guess my alternator is on its way out

 

[buliwyf]

lol good luck man. Mine still hasn't lit up again, so far for about 80 miles now. Maybe something just got wet over the past few rainy days (I hope)

 

[kms1990]

Well that didn't last long lol guess my alternator is on its way out

take your alternator off and take it to your local parts store, they should have a bench tester that they can accurately test it on and tell you if it is good or bad

 

[hotcracker69]

lol good luck man. Mine still hasn't lit up again, so far for about 80 miles now. Maybe something just got wet over the past few rainy days (I hope)

well seem like the issue might have been your belts.

with the rain, the belt might have been slipping causing a voltage drop. when was the last time the belt was replaced? is the tension the belt correct.