Lights dim when bass hits, weird.

**Dillusion** · 07-18-2007, 03:30 AM

I have a 2001 VW Jetta with a custom system, I recently look out my carputer, but recently my lights have been dimming bad when the bass hits. Here is some background info and things i've done:

Setup:
ALpine 9852
4x Infinity 6012i's
12" pioneer sub 4ga wiring
800w pioneer amp for sub
1.5F cap in the line

The problem:
My lights dim when the bass hits for my speakers, not my sub. Its weird as hell. I can turn my sub down to zero, and keep my speakers at 0 or +2 or -2, and my lights will dim. Even if the sub's RCA's are disconnected, the bass hits for the speakers cause the lights to dimm. ALL the lights dim, rear, headlights, dash, internal lights, etc.

Heres what I've done:
Rewired the whole car twice.
Upgraded alternator from 90A to 120A
New starter
Redid sub wire with brand new 4GA
grounded everything to bare metal (HU, sub, all electronics in the car)
DID THE BIG THREE (upgraded ground wires in engine to 0GA)
Fused yellow and red wires in the HU harness @ 10A
Checked speaker wiring to make sure right/left and ground/pwr isnt switched around

Last thing I can think of is to buy an optima yellowtop, but I dont see the need for that as its not even the sub thats doing it. I'm convinced there is a bad ground somewhere int he vehicle or some sort of other electrical problem somewhere.

**DarquePervert** · 07-18-2007, 06:14 AM

Originally Posted by Dillusion

Last thing I can think of is to buy an optima yellowtop, but I dont see the need for that as its not even the sub thats doing it. I'm convinced there is a bad ground somewhere int he vehicle or some sort of other electrical problem somewhere.

I'm not the expert, but i think that you're wrong about your assesment.
It isn't the sub that's drqing the power, but the sub amp. It's drawing power from the battery, so that's pretty obviously the weak link in the chain.

Someone with more experience than I will correct me if I'm wrong.

**durwood** · 07-18-2007, 07:13 AM

I would have said bad ground on something, either the HU, or the main ground for the vehicle-but you siad you have checked them all. Could be your battery is really weak and it's not doing it's part to help regulate voltage, maybe get it tested. If it's the original battery it's almost 6 years old which is about the lifespan of batteries. If you disconnected the signal going to the sub amp then its definitely not the sub amp right now.

Just curious, do you have bose or monsoon in your Jetta? If so, how did you bypass it or are you integrating the factory amp if you do have bose or monsoon?

**TheLlama** · 07-18-2007, 07:35 AM

Probably need a beefier alternator. Your sub amp is drawing too much current.

-llama

**mrhonnesty99** · 07-18-2007, 08:35 AM

Originally Posted by TheLlama

Probably need a beefier alternator. Your sub amp is drawing too much current.

-llama

he has Upgraded the alternator from 90A to 120A(just my 2 cen)

**mezz64** · 07-18-2007, 08:46 AM

With no amplifier's connected at all, not just receiving no signal, does it still happen? If it's an after market HU, does putting the stock one back in produce the same results?

**monkeyracer** · 07-18-2007, 04:45 PM

Originally Posted by DarquePervert

I'm not the expert, but i think that you're wrong about your assesment.
It isn't the sub that's drqing the power, but the sub amp. It's drawing power from the battery, so that's pretty obviously the weak link in the chain.

Someone with more experience than I will correct me if I'm wrong.

drawing power from the alternator, you mean.

When the car is running, the battery is not being used, actually the alternator recharges the energy used to start the car.

There are too many variables to just say it's one thing or the other. If the amp rca's are disconnected, it shouldn't/wouldn't be the amp.

Does it dim when the volume is turned down low or all the way up? If it does it when it's low, then something is drawing too much current. Start disconnecting everything and reconnect in intervals to weed out the power hungry monster in your car.

Also, If it was re-wired incorrectly, you could have crossed a wire somewhere. I don't know your experience level with wiring or electricity, but that would be something to consider.

Have you estimated the power draw for your system to see if the 120A alternator is even enough?

**iamgnat** · 07-18-2007, 06:26 PM

Originally Posted by monkeyracer

drawing power from the alternator, you mean.

Actually, if the Alt can't keep up with the demand then the battery is used as well. This is usually happening when you get a dimming effect.

Have you estimated the power draw for your system to see if the 120A alternator is even enough?

120 should be more than enough for that system. My guess (as has been mentioned already) is that the battery is old and not holding it's charge very well any more. This is causing the Alt to put out it's entire capacity to try and charge the battery (on top of the other load).

Another possibility is that your Amp or HU have some issue and need to be repaired. Try disconnecting the Amp (e.g. no power) and see if the problem persists. If so, try swapping in another HU and see what happens.

-dave

**Nomader** · 07-18-2007, 06:35 PM

from the little I know about car audio, i believe that Capacitors are used for the exact problem you have...they store power when the sub is not pushed, and when needed the power is drawn from them instead directly from the battery.

**monkeyracer** · 07-18-2007, 08:49 PM

the problem with some/most caps is that the power that they store is for a big bass hit, but most music is rhythmic bass hits, and the cap has a hard time keeping up with it. Even 1 farad and more caps will have a hard time with that kind of listening.

The battery being upgraded will help as iamgnat said since it will allow the alternator to focus it's current on running equipment rather than charging the battery back up.