Thread: Stereo System Thumping = Lights Dimming?

Originally Posted by KeithGTP03

I had many grounding points..even the frame. Would still dim at idle. Even running just a JL 500w slash amp.

Well...I say it a lot: There's a guy I know who runs sine waves for competitions w/his 2.5kw setup and he uses a stock alternator just fine. That's the type of load that dynamic music will never see; especially at 500w. Maybe the alt. was on the way out?

No...3 different vehicles and 3 different years. All same result. Ive ran anywhere from 500w up to 2800w, 5 farad caps, 1 farad caps. Could never cure the dimming at idle issue. Closest I got was adding an isolator and secondary battery. Where on other vehicles, running the same outfit, lights would not dim.

cheapest way is to go to a auto wrecker and find a old impala cop car they have a heavyduty alternator and will only cost you like 30-50 bucks

The draw or load at certain moments may be different, but many performance cars running multiple high output systems such as boost a pumps, msd dis4, sometimes 2+ intercooler pumps and other crap that draws a lot use stock alternators just fine. 10ga. wiring from the alternator to post, or your big 3 and then a volt booster, usually the s2 version or whatever.

There is also the idle tables for alternator output like below, if the number is below this the alternator is commanded off -
Accessories -> ALT -> Alternator RPM Cutout
File Location: C:\Documents and Settings\Administrator\Desktop\BINS\01_GTP_BIN_STO CK__original_.bin

RPM Trans Not Trans Enga
0 0 0
100 50 50
200 100 100
300 200 200
400 250 250
500 300 300
600 500 500
700 525 525
800 550 550
900 650 650
1000 750 700
1100 900 700
1200 950 725
1300 950 825
1400 1000 925
1500 1200 1100
1600 1300 1200
1700 1400 1300
1800 1500 1400
1900 1600 1500
2000 1700 1600



[TinyTunerData]
0,0
50,50
100,100
200,200
250,250
300,300
500,500
525,525
550,550
650,650
750,700
900,700
950,725
950,825
1000,925
1200,1100
1300,1200
1400,1300
1500,1400
1600,1500
1700,1600

Originally Posted by thegipper

I've been told that adding a HO alternator will NOT fix the problem. I also have this problem and was told by many that what I need to do is check the grounds on the car and clean them up. If it still dims, then you need to install a 10 gauge wire from the neg battery terminal to the chassis. Also add a 4 gauge wire from the neg battery terminal to the transmission case. This will help ground the battery better thus eliminating the dimming of the lights.

I haven't tried it yet but I will report back after it do it. I can assure you that adding a cap will NOT help as I already have a 2 farad capacitor and it still dims. I do NOT have a cheap amp either. I'm only running a 1k watt mono block to a single JL audio 10w3.

Hope this helps.

Thanks. Let me know the outcome. It's been bugging me for quite some time now.

Turn the music down or bass down problem fixed

Originally Posted by thegipper

install a 10 gauge wire from the neg battery terminal to the chassis. Also add a 4 gauge wire from the neg battery terminal to the transmission case.

Hope this helps.

10 gauge seems awful small to help. Im running 4 gauge from post to frame. Havent tried an additional ground from post because it doesnt seem necessary. Im pretty sure the HO alternator will solve it all, but I havent been able to get my hands on one. I was shown a site yesterday for one, but it said for years 97-02 and I will not purchase another thing for an 03 that says that, as everything the says 97-02 hasnt worked yet

ya 10 gauge isnt gonna do a whole lot

run 10 guage.... speaker wire maybe, definantly not power or ground.

Unless you actually meant 1/0 gauge...but then you'd wanna make sure your power is ot gauge too. But I still dont think its a ground issue

maybe not a ground issue rather an insufficient ground

Its well documented of these cars and their bad grounds...but you can not track them all down. Every Gp Ive owned has dimmed under amp loads. I would like 1-800 to post the setup of the friend thats runnin the 2500 watts with no dim on a stock alt. And how the dimming was solved. ( without auxiliary batteries)

Originally Posted by KeithGTP03

Its well documented of these cars and their bad grounds...but you can not track them all down. Every Gp Ive owned has dimmed under amp loads. I would like 1-800 to post the setup of the friend thats runnin the 2500 watts with no dim on a stock alt. And how the dimming was solved. ( without auxiliary batteries)

There's no secret to his setup. He has 4 1/0 runs to his trunk and did the big 3. He has an extra battery in the trunk but that's for the competitions where the engine is off. Just as it's been mentioned already, grounds are typically insufficient; quality vs. quantity.

Surface contact, locations of actual groundings, corrosion, proper crimps/soldering, etc. These are all issues related to insufficent grounds...even nickel plating copper wire. Personally, I have run class a/b amps that presumed output of almost 1500 watts altgether. I did not have dimming issues unless clipping sub signals. I upgraded the battery to fender ground and added an 8awg wire to a strut bolt. The amps in the rear are grounded to the strut tower bolt as well. Since then I've moved to a new class D amp that is 150x6. It's been tested to put out almost 186 per channel and 192watts a-weighted.

Anyways, I don't have dimming issues. But I've even gone as far as using large washers and scraping off paint in order to increase surface contact for my grounding points. The other guy I mentioned used 1/0 wire from the welding section in lowes or something rather when he did big 3. I've posted his process for melting solder between the wire and terminals too if you feel like searching.

scratch that. i have very slight dimming isses when idling at ~700rpms. It was getting that low when my egr valve was problematic. But then again, even the fan blower was having problems with output at that low an rpm. Also, I had calculated ~30 to 40amps worth of draw, depnding on music, with the class a/b amps and my head unit cranked. The amplifiers' internal fusing combined for 170amps total. I had the 4awg wire for power fused at 80amps next to the battery. Just because you're rated for 728448 jigawatts doesn't mean you're using it. Oh...and a-weighted i was hitting ~115db's and I could get as high as 130's for c-weighted.

My post about capacitors. CLICK.

Originally Posted by zx7r4u2nv

^^^^^ good setup. Ya, dimming lights could be many issues but usually not enough power on supply.

You can only pull what the system is grounded for. If you pull more than that your voltage can bottom out...causing your lights to dim.

Odd I have a Regal and did my first stereo install ever. No dimming no matter how hard I'm pushing it and ....I can't get much past half in fear of blood running out my ears.

Clearly I didn't go with the highest end equipment, it's more than I can use and got the attention of the tint installer who had been into audio installs etc for years. Guy is around 50 years old.

Quality of cabling used can have a lot to do with it from what I've seen. Yes, my install cabling cost me a little more than $300. No dimming, no humming, no issues at all.

KnuKonceptz for all the cabling etc
Pioneer PT3200BT headunit (I know..but it's good for my needs)
Boston Acoustic 5 channel amp. Right one amp with discrete channels for everything.
Middle of the road Boston Acoustic front components and rear speakers
Top of the line Boston Acoustic sub in self made box.

Maybe I'm not pushing the bass you are trying to..maybe my equipment is that much more efficient. I can't imagine a Sony Xplode is very efficient.

Originally Posted by That Canadian Guy

i like the cap idea..........

have you seen a cap that will work for a power rail?

they're quite big...

but 150 V 1200 uF aka 1.2 Farads in multiples is what sits in my cheapo amp.

The original use of capacitors was on the lighting circuit in vehicles for sound quality competitions. The voltage regulator didn't always keep up with the electrical needs of the system. So the capacitors were soldered for use on a bread board and hooked in-line with the circuit for lights in the vehicle.