battery gauge problem,

stackedstangs · Apr 30, 2013

For some reason my battery gauge drops when my lights and stereo are on. Then when I turn my air on it goes down even more to where its almost on L. Anyone else have this happen?

sorry about all the electrical questions... I can build a motor in a weekend but when it comes to wires I get lost.

alt and battery are good. Grounds seem good from what can tell.

DeepList · May 1, 2013

I wouldn't really trust that idiot gauge. It's rather pointless. Have you tried using an accurate voltmeter to see what the actual voltages are?

CC'S95GT · May 1, 2013

What did you do to know the battery and Alt is good?
How big of stereo?
Put the volt meter on VDC and connect them to battery. Red lead to + post and black lead to - post.
The reading should be above 14 volts. Rev the engine a little and make sure the meter bounces back to the origional reading.
Now turn on you lights, what's the reading? now the radio, what's the reading.
Sometimes Alts don't show signs of failing till they get hot. If you has it tested at the parts house then it may not have ran long enough.

You coyuld also have corrosion inside of the Alt cable restricting the full output of the Alt.

ttocs · May 1, 2013

its because of your under driver pullies..... You either need to bump the idle up a little bit or just deal with it. Also save a few bucks for when your alt goes out as it causes them to run hot and burn out sooner then normal.

stackedstangs · May 1, 2013

oh sorry i should have said my 98, my 1998 does not have pullies and the stereo is a kenwood but very simple. no tv screens here

. and ill see what it reads today.

ttocs · May 1, 2013

oh then remove and clean all ground connections, if there are still problems have your alt/battery tested.

MustangChris · May 1, 2013

get a volt meter on it.

If you need help buying/using a volt meter, we're here to help!

stackedstangs · May 1, 2013

my volt meter is dead, i used it like 3 weeks ago but now nothin.. any particular brands that are good? i had a cheap one from o'reilly's for 15ish bucks

MustangChris · May 1, 2013

volt meters can get litterally as pricey as you want. Electrical engineers use $500.00 volt meters...

Instead of hitting auto parts store, maybe hit Home Depot. Their's may be more heavy-duty in order to handle housing problems opposed to just a lil' ol' car battery. lol.

CC'S95GT · May 1, 2013

maybe the battery on the volt meter is dead or the fuse is blown.

joekd · May 1, 2013

For battery troubleshooting I use the free multimeters from harbor freight. All they need to do is show DC voltage

ttocs · May 1, 2013

probably just a blown fuse on the meter. Its easy to do if you had it set to measure current and didn't put it in series in the circuit to measure. Really a meter will not tell you a whole lot here though you can get 14v out of the alt but still not have the current supply necessary to drive everything. Your best bet is to take the car in and have the alt/battery tested although the best way to test the battery is to take it out and leave it with them for a few hours.

RichV · May 1, 2013

I have a handly little voltmeter gauge that plugs into a lighter socket, has a digital display of volts. It was real inexpensive and works well. Plug one of those in there and test like CC stated. If you don't want to buy a real meter. Your $15 cheepie should work just fine, check the bateries in it. Probably just dead.

Also, my battery chager has a aternator test mode on it. Check if yours does too, it will tell you if the alternator is good. You should read around 14 volts at all times when the car is running.

Something to check real quick is the little white wire on the alternator, not sure if the 4.6 cars have it, but my 94 does. It had unplugged on me once and caused charging issues.

stackedstangs · May 6, 2013

it was reading fine when i tested it. but now i have another problem.

DeepList · May 6, 2013

stackedstangs said:
now i have another problem.

And what would that be?

stackedstangs · May 6, 2013

transmission problem. I posted in the 4.6 2v specific, o/d light is flashing and its hard shifting, slipping a little bit. p0108 and p1702 are the codes that are being thrown. either a bad sensor or a bad transmission.