Alternator Question


Feb 3, 2011
My 2002 Gt is not keeping charge due to my steeda UDPs. I was told I need a higher amp alternator to compensate. What size is stock? What size do I need? I don't have anything crazy in my car, no amps subs etc... Thanks!!
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Anyone? I really need some direction...I have found out that the stock alternator is 110 amps so I need to know what size to replace it with to avoid having the battery drain on me.
the battery and the alternator have both been tested. I was told both are good. I was also informed that the underdrive pulleys are causing the alternator to not properly charge the battery enough because if I sit at a red light while its raining with my radio, lights and windshield wipers on the battery gauge drops unless I rev my engine in neutral. I don't have anything crazy in my car I have a replacement deck with the factory equivalent speakers.I've never had any overheating problems.
Maybe try putting the stock pulleys back on and see if that fixes it. If it does, I would weigh the advantages of underdriven pulleys versus having to fix the issue. I had pulleys before my blower install. I was not impressed by any change they made.
Higher amp alternators are not the cure because they still require a minimum RPM in order to create power.

The issue here is that your current alternator is spinning too slowly to produce a proper charge. Going to a higher amp alternator may not fix the issue of your accessory belt is still spinning too slowly to fix that issue.

You have 2 solutions:

1) find a set of stock pulleys and swap them back on

2) Find a stock alt pulley, or an aftermarket alt pulley that will fit of larger diameter in order to OVERDRIVE the alternator and compensate for the slowed down accessory system.

A 3rd option is to find an aftermarket alternator that produces full power at a lower RPM than stock. You'd need to know crank pulley size and alt pulley size and do a little bit of math to calculate if this will work.

Option 1 is prob the easiest