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Low alternator output at idle?

Old 01-18-2004, 08:24 AM
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I don't have anything installed in my system right now due to the temperatures outside, but I have made some observations regarding my electrical system..

When idling, my headlights appear to be fine, but as soon as I bring the engine up a couple hundred RPM, they brighten up. Same thing goes for my fan. It gets a little louder as soon as I accelerate. Even depressing the brake peddle will dim the lights, and slow the fan. My power windows will cause all the same effects at idle.

Is this due to my alternator? I believe it is a 70amp alternator in the 1.6EL. I have had light dimming problems with previous amplifiers I've owned. The only electrical upgrade I've done is a optima deep cycle battery.

Any suggestions?
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Old 01-18-2004, 08:31 AM
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Wink

I haven't seen a car that doesn't do that.
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Old 01-18-2004, 09:27 AM
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I've got a high output alternator rated for 130amps and at idle with everything electrical turned off even the simple turn signal will behave slugishly.
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Old 01-18-2004, 10:09 AM
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the cold might have an effect as well...

try it again when its on the plus side of zero see if there is a diff
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Old 01-18-2004, 10:30 AM
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That's what happens to mine as weel, and I have an upgraded nissan alt, to what I was using before. Not to mention heat get's colder when at idle...lol.
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Old 01-18-2004, 12:55 PM
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That is normal and expected. This is how old timer mechanics could test if you had an alternator or battery problem (without test gear). Rev the engine and if the lights intensity changes your alternator is good and the battery is bad, no intensity shift and itís the alternator.
The amount of Power a generator can produce is determined by the prime mover (belt driven). So at slow speeds the generator though rated for high power is limited by RPM.
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Old 01-18-2004, 12:58 PM
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This is also why the lights dim on bass hits when the engine is idling. If you lights dim while driving you have a supply and demand problem (or a faulty electrical system)
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Old 01-18-2004, 08:04 PM
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Glad to see I'm not alone [img]smile.gif[/img]

Thanks for the feedback..
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