Battery dash light on

Sonic04GT · Apr 7, 2011

My battery light just came on. Drove the car a few miles with the headlights, radio, etc and the battery gauge appeared to be holding steady. I just replaced the alternator the last time the light came on maybe 2 years ago. Car has 58k on it and was replaced maybe 10k ago. Wtf...I've had no problems with this car and now maybe a second alternator?

Is there anything else this light could mean? Predator is showing no codes. Predator read about 12V I believe. Can check with a multi-meter tomorrow.

What specs on the factory alternator? I think I saw one on craigslist the other day that was like new. Wouldn't hurt to start looking.

And I'm making a damn road trip on monday.

I disconnected the negative battery cable a few times the other day to install/work on my wideband AF gauge. Was fine up until tonight. Connection on the terminal looks good, but it's also dark out.
Also have underdrive pullies but have never been a problem.,

Sonic04GT · Apr 7, 2011

Well, um...I started the car, light was still on. Took a look with my flashlight as I had to drive the car home anyway. Pushed on the 2 harnesses, got back in the car and the light was off. Odd...

Maybe my ears are messing with me but I think I hear a slight whine, and inside the car, when I give it gas the whine seems to change tones, like it may be coming from the speakers. Very faint.

joshjwc9 · Apr 7, 2011

Did this start after the install of the wideband? If so, it could be the alternator which may just give feedback through the speakers, or the radio having a wire loose that is grounding out.

Take your alternator and/or battery and have them tested. Someone will chime in with AC ripple soon I bet..

Sonic04GT · Apr 8, 2011

joshjwc9 said:
Did this start after the install of the wideband? If so, it could be the alternator which may just give feedback through the speakers, or the radio having a wire loose that is grounding out.

Take your alternator and/or battery and have them tested. Someone will chime in with AC ripple soon I bet..

Well I installed the wideband on monday and this just happened tonight, then went away. I used existing wires from my narrowband. All I did was splice them with bullet connectors and then ran the O2 sensor cable.

Where would I check for the wire loose on the radio? If the headunit only, I crimped them all myself, on an Alpine headunit. Installed that a few months ago. I ran the O2 sensor cable underneath the stereo but shouldn't have had any affect. It's beside the shifter and then out by the pedals so it's not really even close.

Sonic04GT · Apr 9, 2011

Light just came back on today. Hooked the meter up immediately and it's not charging the battery.

Is there a way to test the alternator itself so that I can rule out a fault cable harness? I was just measuring from the battery terminals.

Revving the car made no difference in voltage.

Edit - Found the receipt. Only a year and a half old and I guess it's covered by an Autozone lifetime warranty. I'll try to get a new one tomorrow. Hopefully I can get my underdrive pulley off of it and get the stock one back on in an unnoticeable fashion.

Update - Autozone swapped them out with no questions asked. Thanks Autozone! Car is again working fine.

Night Shifter · Apr 11, 2011

FWIW my battery light came on a day after i loaded my tune from AM a few years back... sometimes it would stay on sometimes it would occasionally flicker and sometimes it wouldnt even show up....checked all grounds, replaced battery, had my alternator checked.everything check out so i assumed it has something to do with the tune/tuner but to this day, even with a new set up and new tune it still shows up every now and then...ive gave up on it and just figured it as being a little battery light demon lol

however, the floater in my coolant tank went bad causing my car to throw the low coolant light so i unplugged it a while back and ive noticed in the rain or at the car wash if the connector gets wet it will throw a low coolant light until i plow out the plug/dry it.....so maybe something is getting wet sensor wise with our battery connection?

id take your alt and have it checked just for a precaution. its a free check at any napa, autozone, or advanced

*EDIT* i should have read your last post lol

trinity_gt · Apr 11, 2011

The slight whine you're hearing in the speakers is likely a sign that the rectifier block in the alternator is toast. One or more windings is likely open leading to a very high amount of ripple (voltage variations) that is being telegraphed through the radio and amplifier power supplies and ultimately to the speakers.

Put your meter on "AC volts" and report what you are seeing (note: to be of any use the meter must be a so-called "true RMS" meter or the AC reading will be meaningless...)

EDIT: Oops...didn't notice you had it fixed.

1999MustangSLP · Apr 25, 2011

if you have an aftermarket antenna make sure the ball on the top didnt fall off. This has happened to all of my antennas after driving it through the car wash. This then creates a whining noise, almost sounds like a turbo lol

Battery dash light on

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