2009 sedan, 4.6 charging system fault?

[themandrew]

Hello, first time on the forum
I have a 2009 genesis sedan, 4.6, battery light is on. Voltage at battery at alternator are good.
When the car is running, my rear defrost, and heated seats will not turn on, and the stereo produces the turn on engine to save battery life, like if the car was in the on position with the stereo running.
Any leads on what the heck is going on?
Heated seats and defrost will work momentarily when the car first starts, than the battery light comes on and they no longer work.

 

[joegr]

You say that the voltage is good. Exactly what is it reading?

 

[themandrew]

You say that the voltage is good. Exactly what is it reading?

I can't remember the numbers currently. I'll get them tonight. The car has been driving for a few weeks like this, if the charging system wasn't working the battery likely would have died I'd think.

 

[Shady_panda]

did you replace the alternator with an 3rd party one? mine was going boinker when I did it, got an OEM from ebay and it goes away.

 

[Gunkk]

Hello, first time on the forum
I have a 2009 genesis sedan, 4.6, battery light is on. Voltage at battery at alternator are good.
When the car is running, my rear defrost, and heated seats will not turn on, and the stereo produces the turn on engine to save battery life, like if the car was in the on position with the stereo running.
Any leads on what the heck is going on?
Heated seats and defrost will work momentarily when the car first starts, than the battery light comes on and they no longer work.

to the forum.

Yes when a charging system fault is detected and red dash light illuminates, the BCM disables all those high draw features to avoid stranding you and gives the car a chance to make it to your mechanic before the battery dies. While it might be a false alarm, my guess is that it's a legitimate charging system problem. Usually the alternator is the failure, but it's a 15 year old car so wiring and terminations should always be considered, especially if it's a rust belt car. For example, a rusted/high resistance circuit might have enough voltage drop on the sensed circuit to trigger the fault, even if the alternator is fine and battery is still getting some volts.

I recommend that you take the car to your mechanic and get your charging system diagnosed and repaired, whatever the fault.

 

[themandrew]

did you replace the alternator with an 3rd party one? mine was going boinker when I did it, got an OEM from ebay and it goes away.

Have not touched the alternator before.

 

[themandrew]

to the forum.

Yes when a charging system fault is detected and red dash light illuminates, the BCM disables all those high draw features to avoid stranding you and gives the car a chance to make it to your mechanic before the battery dies. While it might be a false alarm, my guess is that it's a legitimate charging system problem. Usually the alternator is the failure, but it's a 15 year old car so wiring and terminations should always be considered, especially if it's a rust belt car. For example, a rusted/high resistance circuit might have enough voltage drop on the sensed circuit to trigger the fault, even if the alternator is fine and battery is still getting some volts.

I recommend that you take the car to your mechanic and get your charging system diagnosed and repaired, whatever the fault.

Coastal area, so definitely rusty. The thing that throws me for a loop is that while the engine is running, and driving around, I am prompted by the stereo to turn the engine on to save the battery.

 

[joegr]

I can't remember the numbers currently. I'll get them tonight. The car has been driving for a few weeks like this, if the charging system wasn't working the battery likely would have died I'd think.

Do you remember if they were over 13.8v, or ideally around 14.0 to 14.2 volts?

 

[themandrew]

Do you remember if they were over 13.8v, or ideally around 14.0 to 14.2 volts?

Alternator tested between 13.8-14.2 (I was testing in a sh**ty code reader)
Battery tested low at 12.10
Again the only thing throwing me for a loop is the message on the stereo. Why does it think it's not running? Or is the battery that low that it thinks the car is off?

 

[mikec]

Go to the battery in the trunk and look at the positive cable. You'll see a secondary cable attached to it. This secondary cable has its own fuse or similar gizmo at one end. If this cable goes bad, a lot of the car stuff does not see normal voltages.

I would also double-check all fuses and make sure they fit tightly to their contacts. It is possible a "sense" function in the BCM is thinking "not being charged" because some fuse or diode has crapped out.

mike c.

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[joegr]

Alternator tested between 13.8-14.2 (I was testing in a sh**ty code reader)
Battery tested low at 12.10
Again the only thing throwing me for a loop is the message on the stereo. Why does it think it's not running? Or is the battery that low that it thinks the car is off?

Is 12.1 at the battery with the car running? That's very bad if so. Even with the car off, 12.1V is a pretty low reading. Either it's not really getting charged, the battery is bad, or you have a very high parasitic drain. My guess would be that it's not really getting charged, since the car is already trying to tell you that.

 

[themandrew]

Well folks turns out I'm not the brightest bulb... when checking the fuses on the battery like mikec suggested I noticed there was a post with nothing attached...
Plugged the loose wire in... problem solved... don't worry I've done some face palming. Thanks a tonne to all who helped.

 

[Charlie1982]

Well folks turns out I'm not the brightest bulb... when checking the fuses on the battery like mikec suggested I noticed there was a post with nothing attached...
Plugged the loose wire in... problem solved... don't worry I've done some face palming. Thanks a tonne to all who helped.

Hey, at least it was a cheap fix! Glad you're up and running again...

 

[Gunkk]

Well done!