alternator problems?

[Crazybiker420]

when i rev over 3k my lights dim and the battery light comes on. the second it goes under it goes back to normal, what the heck is going on? im thinking about replacing the alternator tomorrow, but im not sure.

 

[melsg5]

have you tested the alternator with a voltmeter?

 

[Crazybiker420]

i have not, but at low rpms everything functions normal, how would i be able to test it? i dont really have a voltmeter to use, :/

 

[melsg5]

you need to test the voltage output to determine if the problem is the alternator

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[Crazybiker420]

what are some of the other problems it could be? i do have a battery cap hooked up for my subwoofer. im going to unhook that tomorrow to see it its bad. but what systems in the car activate/deactivate at exactly 3100 rpms?

 

[Crazybiker420]

honestly where i get parts it would be cheaper for me to just replace the alternator than to test it.

 

[Grue]

honestly where i get parts it would be cheaper for me to just replace the alternator than to test it.

AutoZone does alternator testing for free, as do a number of other places. You should test it even if you think it is the culprit as to make certain it isn't something else at fault. Furthermore, usually when an alternator goes the vehicle will not charge properly at lower RPM instead of the other way around, as you are experiencing. Of course it could be so far gone that spinning it up faster no longer yields a meaningful charge...

It could be a number of things, including even the battery if its old.

In any case, get your alternator tested first.

 

[Crazybiker420]

so i went and got a used alternator for $20 and it fixed the problem. thanks for your help guys!

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