My battery light is on


Asked by Jun 24, 2013 at 11:50 PM about the 2002 Ford Mustang Base

Question type: Maintenance & Repair

I needed a new alternator for my basic 2002 ford mustang so I got a rebuilt one now my battery light is on. I took it to autozone to be tested and they said the alternator is fine but my battery was low. I had to get it jumped twice. So I  got a new battery. That light comes on then stays on now my new battery is dead so I need a jump again. Is it the voltage regulator? the fan belt seems fine

6 Answers

check connection at the other end of the black cable what connects to the chassis/ground....make sure it's comfortable with pullin' 300 cca~

3 out of 3 people think this is helpful.

the 1/0 battery cable to the engine block (near the alternator) should be tended to as well~

James Ramond

if the light is on its not getting voltage period, those testers don't cover dodge I know, read the literature ford may be like dodge ,testers are outdated I guess, unless wires were put wrong by you witch I doubt . in my case I said give one to try and after they did the tested one proved to not show. the instructions also stated such! who reads instructions anyway ,not me or them apparently !

1 out of 1 people think this is helpful.
Tracy Hooks

Typically, the battery light on is an alternator concern. While the test is simple, accessing the back of the alternator while the engine is running can be tricky. First, charge the battery - don't try to make the alternator do it - that's how most alternators end up failing prematurely. Next, hook up a VAT40 or equivalent tester, see that the alternator isn't charging then, short the "Test Here" screw to ground and watch the tester. What you are doing is bypassing the regulator and giving the alternator Full Field - max power so to speak. If your readings change to the max output of the alternator, the regulator/brush set has failed. If not, the armature has failed. If you can access an oscilloscope, you can check the diode-trio too. Sounds complicated but if you spend a couple of bucks with a shop that knows their stuff, they can diagnose your troubles quickly and accurately - or you can throw more money at it.


Thanks guys, I will get it all checked out and let you know the outcome

1 out of 1 people think this is helpful.

most likely you have a bad alt,check the connector at the regulator on alt,this is the most common concern,hope this helps

2 out of 2 people think this is helpful.

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