Question about 2004 Pontiac Grand Am

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Fluxuation in electrical power

With heater on high, fan slows head lights dim a little as well as dash lights....have replaced alternator, battery is in good condition. this only takes place once vehicle comes down to a idle with the brake pedal applied.

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This is normal behavior in Grand Ams. I've had a '97 and a '04 and both did this from day 1. You'll also notice the lights dim/blower slow down more if you press the brake pedal while idling w/ blower on high and lights on; it's just that the alternator on these cars can't output anywhere near full power at idle. (my '03 S-10 also does this). Watch your voltmeter if you have one, when running above 1200 RPM you should see the system running between 13.5 - 14.5 (usually you just have to eyeball this as the gauges aren't well marked, mine are only marked 8 & 18 - should read slightly past halfway). If you're still worried, have someone check the system for you, many places like Autozone or Advanced will do this for free.

Posted on Feb 05, 2009

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