The battery in my '99 mustang GT was replaced not too long ago, and I'm experiencing a problem with the battery warning light in my car that started on 07.15.04. The light had flickered on and off a little during lunch hr at work, but after work for the 20 min car drive home the battery warning light stayed on during acceleration and cruise. So if I took it out of gear the light would go off, I'm assuming because of idle. I'm just a kid still I s'pose at the age of 21, but can anyone tell me if this warning light is coming on because of a loose belt? The engine almost has 55k mi on it. And the battery is not a cheap brand, I think it is interstate and about 6 months old. It seems as though when the rpms reach 1200+ the battery light comes on and stays on until it drops below that 1200rpm mark. I'm going to go down to advance auto parts and test the battery and alternator but I don't think either have gone bad. If I push onto the belt to see the tension, I can push it about 1/4-1/2 an inch, but not too sure on the exact measurment or what it should be at. If you could provide me with any information or knowledge I would greatly appreciate it. The belt looks new still, even tho the 55k mi.

God bless & g'day



....if I had the money to, I would drive my '66 mustang to work and school every day. but the '99 is okay, just picky as it seems.

 

Belt should be WAY tighter. Replace it.

Also, have your tensioner looked at. It's possible your belt is slipping and undercharging your battery under load.

 

Same thing with mine, we jsut put the car back together and ran it, and the battery we had in there was nearly dead. took forever to start, and all the lights were dim as ****. Also, the needles swept each time i turned the key.

Put a new one in and everything is fine, but the light is still on. WTF??

 

Serp belts can have up to 1/2" of deflection. However, if your battery light is coming on like that take it to Advanced and have them test your alternator. If it comes back okay get a new belt and tensioner.