dimming after new alt and finished big 3 but not before

[darren700 10+ year member]

ok, heres the deal, about two weeks ago my battery died, got a new one, died in two days, so the problem was the altenator. i went to the place where i got my battery (insterstate) and they said theyd build me a 160a alt for $150 cdn, they did and i installed it. i also finished my big 3 upgrade and added a 2.4 farad cap to the system. now the strange part, before i never noticed any dimming period.. never.. now when im idleing at a light (around 700rpm on the cavi) i get severe dimming in dome lights and headlights. as soon as i bring it up to 1000rpm the dimming goes away, unless have it cranked then i notice it again. the thing that confuses me is that with my old battery and alternator (105a stock) i never had any dimming problems but now i do... im lost as to why this is happening....thanks for any help

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[60ndown 10+ year member]

maybe your new alt does its 160 amps @ 2000 rpm and less than your origional alt at idle? bummer

 

[darren700 10+ year member]

i was thinkin that.. but is there a way i can change that? cause now everytime i stop i have to turn down the stereo or my fronts even start to clip from low voltage

 

[60ndown 10+ year member]

change the pully size?

 

[darren700 10+ year member]

would putting a smaller pulley on overload the alternator at the higher rpms though?

 

[MegaHurtz 10+ year member]

Pulley size won't completely remedy the problem, it may only slightly help.

I'm guessing they used big thick copper wire to build your stator... when companies do that, it kills the idle performance of the alt, regardless of the size of pulley used.

I'm going to conclude that your only solution would be to have your alt rebuilt to a better spec. I've got a 180a in my car (we build HO alt), and it works awesome at idle. I can get you a pulley if you want to try one, probably $20 + ship. Send me a PM if you want one.