02 wrx Strange dimming problem

[scythenkai]

Hey, my 02 wrx is modded with TBE , uppipe, turboXS TMIC, perrin intercooler tubing and flash to cobbstage2.
I also have a gel type lite weight battery. I have been noticing while driving, if i let off the accelerator my heater fan will slow and headlights will dim down for a split second. It doesnt seem like any of the interior lights are dimming. There is no difference wether or not the heater is on.

My original thought is to check grounds if that is not the case where else should i look?

[DNO505]

i have an 03. same thing happens to me. no idea why?

[scythenkai]

I check all the grounds and they are all connected securly with no corrosion.
Do you have a liteweight gel battery too or regular battery?

[nagyhead]

its most likely the alternator or the battery. Have a charging system test done to be sure.

[RentForSale]

Id also say alternato
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