bad wiring or bad alt?

my lights dim, once about every 5 seconds, they only do it when my cd deck is on, i can mute/pause the deck and the lights still do it, EVERY light in my car does it, headlights,dome light, and etc. its a 1997 vw golf trek, the cap likes to sit at 12volts for a second, then it drops slowly to 9volts or so, then shoots back to 12, then shuts off and beeps, so yeah somethings wrong as can be plainly seen it use to do 14volts/13.75 on the cap, but lately its stayed around 12... i think ima do the big 3 if i can get my hands on some bigger wires but any ideas on what would cause this?

ive only 1 amp, a hifonics brutus 1606d, and 2 type-rs so you think its the amp thats causing this? what would i have to replace? im going to look into it tommorow, didnt realize it was doing this till it was dark, and it was starting to snowstorm(yet again, weather cant make up its mind) if its the amp i swear ima be "angry"... i just sent the old one back because it fried, and erg...

Remove the fuse from it and see. There is NO way your deck is pulling enough current to do this. So if it only happens when your deck is turned on, I would have to guess that it is the amp. It should be easy enough to figure it out.

Alrighty, ive been to busy to get down and mess with it, and the weather took a turn for the worse, minnesota cant make up its mind about which season it wants yesterday afternoon the car was fine, the cap showed 13.7 volts average and the lights didnt do the dimming how they did before this morning however, the car did it again, after about 7 minutes(my drive to school)the cap drained all of its power, started beeping, and cut off power to the amp, i couldnt notice the lights dimming since it was morning, but i believe they were doing it, also just an hour ago i was driving and the cap turned off,BUT the amp did not... could it be the cap? i just got a new battery, and the alt seems to be good, and the amp is less than a month old, i litterly just replaced it cuz i fried the last one Im thinking of disconnecting the amp completely from the cap and seeing if it still does it, and working my way slowly around the car pinpointing the source of my power problems... also, since i still have my older battery, and its still good, could i wire that in? or would that be a bad idea, someone told me that they must be the same kind otherwise it will cause problems, im not sure if thats true or not, but id much rather have a second battery than a 1 farad cap -also- if u havent noticed i ask alot of questions, but im still young and learning and this is a hobby that will stay with me for life, im just doing what i can to learn, and readily admit not being a know-it-all teen like some nowadays

might be a dirty battery connectors? or even a funky alt ground. the ground on the the block of the car will get errrrr funky after a while.OWWWWWWWWWWW you said you discharged the cap!

i just put new battery connectors on though, with my new battery, not sure what brand of battery it is, but the ground part may be right, lately ive hit alot of "puddles" that managed to spray water under my entire hood so when it gets nice ill find the problem, but its spring and the weather persists in being 30 degrees out... from what i heard up north in minnesota got 24+ inches of snow this last weekend...

you also may want to beef op you alt ground im using 2 gauge wire.OWWWWWWWWWWW you said you discharged the cap!

ok, as far as i know ive fixed it, heres what was wrong: where my ground was grounded was TERRIBLE, the previous owner left the ground attached, so i juts used it(bad idea) it was attached to a screw that went into the wheel well, it threw the screw off and allowed water from the roads to get on the ground wiring(he didnt use any sort of connector) so it rusted and corroded... which caused the amp to get power/lose power, receive a little, at random times, and what not i also think my caps wrecked, it doesnt seem to have any charge in it, and wont hold one, but meh, it was a vr3 1 farad, so nothin special so yeah, it was just bad wiring that u had to look "closely" to see(i figured it out when i was checking the wiring, and pushed on the ground, and it turned off the amp, but when i pushed the other way it turned on, and the ground was held tightly, so i took it off and noticed the rust/corrosion on the 4 gauge wire)