4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

Battery light issues

Old 05-29-2007, 06:38 PM
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Join Date: May 2007
Posts: 21
Default Battery light issues

When I first start my stang up the battery light comes on and sometimes stays on (or flickers)while it's idling. Whenever I rev the engine, it goes away for a bit. Also, if I'm doing lots of driving in 5th, the light starts flickering, etc. It goes away when I rev the engine though. I took it to Autozone and had them check out the battery and the altenator, but they said everything was fine!?!?! Any suggestions? I'm at a loss.
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Old 05-29-2007, 07:05 PM
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Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,933
Default RE: Battery light issues

Underdrive pulleys--most reduce the alternator speed by 8% to 10%. Not as much as the other stuff (p/s pump and AC), but slower nonetheless...[/align][/align]from the March FAQ:[/align]
2. "But won't underdrive pulleys cause a charging problem?"

Again that depends on your car and how and when you drive. Automotive manufacturers build a certain amount of extra capacity into their cars for situation of high demand like driving on a cold rainy night with the lights on plus whippers and defrosters going. An older car with a less then optimum charging system and a small weak battery may have charging problems with underdrive pulleys and some cars with monster audio installations require higher that normal electrical demands. A well maintained auto should have no problem at all. Sometimes raising the idle by 100 RPM is all it takes to bring the charging rate back up to normal.

If electrical charging is an issue with your particular application March Performance has a smaller alternator pulley available to increase alternator output but to still allow a HP gain from underdriving the other accessories.
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