Voltage Drops

[jmcs23 10+ year member]

Hello,

So I decided to test my voltage yesterday after dealing with dimming lights and the engine feeling sluggish sometimes while sitting idle with my music playing at loud volume levels.

Here's what I have hooked up in my 2003 Nissan Altima right now. It's my old equipment that I'm using until I can afford all new equipment:

- Amp: Kenwood KAC-729, running at 150 watts RMS x 2 at 2 ohms

- Subs: 2 Sony XS-L151P5

- Wiring: Raptor 4 AWG Power & Ground (I think this may be my problem??)

- Alternator is about 2 years old, I had shop put it in after stock alternator went bad

- Battery is Enegergizer brand I bought from Costco about 2 years ago

- NO big 3 has been done

Here's the voltage readings I was getting with my multimeter at the amp:

- 12.86 with car off and no music

- 14.13 with car on and no music

- Once I started turning the volume up to loud levels the voltage would drop down from anywhere between 13 volts to low 12 volts. When the voltage would drop you could feel it in the engine, it felt sluggish to say the least... If I kept turning the volume up, the amp would eventually go into protect mode I'm assuming because it wasn't getting enough voltage at that point.

I also hooked the multimeter up to the battery terminals while the car was off and got normal readings 12.5-12.8 and when I turned the car on with no music I also got normal reading there 13.8-14.8

I don't understand why that little Kenwood KAC-729 amp would put such a strain on my electrical system. I would hate to see what a "real" amp would do to it.

Since I'm using cheap power and ground wires (Raptor) I wanted to start by replacing those with some high quality brand name cables. Maybe that's the cause of this problem???

Any input or help is appreciated! Thanks!

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[pimpinr]

Your electrical sukcs big time if it can't handle two Sony Subs.

That amp takes 8 gauge wire not 4.

 

[bmk6795 10+ year member]

also do the big 3 with zero gauge wire.

 

[jmcs23 10+ year member]

Your electrical sukcs big time if it can't handle two Sony Subs. That amp takes 8 gauge wire not 4.

So what would you recommend?

I don't see why stock battery and alt can't handle the weak equipment I'm using right now...

Thanks!

 

[jmcs23 10+ year member]

also do the big 3 with zero gauge wire.

So you think getting higher quality power and ground wire and the big 3 would be a good start?

Thanks!

 

[pimpinr]

Do the Big 3.. Get a Nicer Under The Hood Battery and use 8 gauge wire to your amp

 

[jmcs23 10+ year member]

Do the Big 3.. Get a Nicer Under The Hood Battery and use 8 gauge wire to your amp

Alright, thanks for your help. So the 8 AWG wire would provide better voltage to the amp? Or is there some kind of conflict with using 4 AWG wire on an amp that uses 8AWG?

I actually have some 8AWG Rockford Fosgate wires that I can install today.

 

[Chriszle 10+ year member]

Ummmm. Running 300 watts, you do not need to do the big 3. You can, and it won't hurt anything, but I doubt that is the source of the problem. My guess is that you are clipping the **** out of the amp. Read the gain setting tutorial, and go from there.

 

[hispls 5,000+ posts]

I would suggest that your battery is rather weak along with your stock alternator. First thing I'd replace the battery with a good quality AGM and see if that doesn't fix things.

 

[jmcs23 10+ year member]

Ummmm. Running 300 watts, you do not need to do the big 3. You can, and it won't hurt anything, but I doubt that is the source of the problem. My guess is that you are clipping the **** out of the amp. Read the gain setting tutorial, and go from there.

Alright, I've set gains with a DMM so I'll go ahead and do it again...

 

[Chriszle 10+ year member]

The amp shouldn't be drawing more than 30 amps ever. There is something wrong if there is voltage drop like that.

 

[jmcs23 10+ year member]

The amp shouldn't be drawing more than 30 amps ever. There is something wrong if there is voltage drop like that.

Once I go set the gain with a DMM, if I'm still having the same problem what would you suggest?

Do you think running a 8AWG (Rockford Fosgate) power and ground would make any difference?

Do you think it could be a bad ground? I have it sanded and grounded to a seat belt bolt underneath the rear seat.

Thanks again!

 

[Chriszle 10+ year member]

I would double check the gain, and the wiring. It could be a bad battery, but your alt should still be able to keep up with that demand.

 

[jmcs23 10+ year member]

I checked the gain with my multimeter and set it right where it should be. Now the bass ***** :-( and I'm still having the same problem as before...

I'm just confused because when I test right at the battery terminals with the car ON and OFF the voltage levels are within range. It just seems that when I try to use my amp the voltage starts dropping.

I'm going to try the 8 AWG Fosgate power & ground wires I have and see if it make a difference. If that doesn't work, I'll have Autozone test the battery and the alternator...

 

[mlstrass 5,000+ posts]

Take the batt out and have it load tested at an autoparts store. Also how old is the belt, it could be slipping so the alt wouldn't be fully charging...