Dimming at idle.

[Sarthos 10+ year member]

My car has problems with the lights dimming and the voltage dropping when my car is idling. I have a volt meter on my dash and it will say between 13.5-13.8 volts while I'm driving, but as soon as I stop it goes down to 11.9-12.1. If I'm stopped for quite a while it drops down to 11.5 or lower sometimes. I'm just wondering why the heck my system would do this? I have a 170 amp alternator and a Stinger SP1000 battery in the rear, with 1/0 gauge monster wire going from the alternator to the battery, 1/0 monster from the battery to a shiny spot on the engine, and 1/0 monster from the battery to the frame. The voltage also doesn't normally shift when I'm drawing lots of power. If my radio is on 0 and my lights are all off, fans are off, etc. and the meter reads 13.8, I can crank the radio, turn on all my lights (which draws over 400 watts) and fans, etc. without even making a tiny ripple in the voltage. So I'm wondering, could the problem be related to the alternator, the regulator, the battery, the wiring, or is it likely that my underdrive pulley is the culprit? Any suggestions would be greatly appreciated //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

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[jdawg 5,000+ posts]

uhh

whats your stereo consist of?

 

[Sarthos 10+ year member]

Right now there's an Eclipse CD 8100 for my head unit, a 4x100 Planet Audio VX4004 amp (only two channels in use) for my rear two speakers, and a 150x2 Planet Audio BB150.2 amp for my front two speakers. It did the exact same before when I just had the 4x100 amp powering all four speakers and a 1600 watt Planet Audio RXD-2400 amp powering a pair of subs with an Alpine CDA-9883. At that time though I didn't have as many wires, just a 4 gauge from the alternator to the battery in the trunk and a 4 gauge from the battery to the frame.

 

[jdawg 5,000+ posts]

eww, just seen you have an underdrive pulley, probably the problem, actually more than likely, get your alt checked out also

 

[Sarthos 10+ year member]

if the alt were the problem wouldn't that make the car not charge and have problems holding voltage? Never knew for sure if underdrive pulleys would actually mess with voltage, I thought the car's regulator and the higher output on the alternator could take care of whatever change there was?

 

[jdawg 5,000+ posts]

if the alt were the problem wouldn't that make the car not charge and have problems holding voltage? Never knew for sure if underdrive pulleys would actually mess with voltage, I thought the car's regulator and the higher output on the alternator could take care of whatever change there was?

not really, if you have a h/o alt or a rewound one idle voltage can suffer but you get a higher max voltage. And underdrive pulleys, think about it, its spinning slower, it cant make the voltage it would just running on stock pulleys. Why are you running underdrive pulleys anyways? I never really understood this unless you have a drag car or a weekend car. Is the 5hp worth all the hassle and money you spent on them?

 

[Sarthos 10+ year member]

I assumed the high output alternators would have decent idle voltage. I also figured that because the 170 amps is the max rating which is supposed to be 1600 RPMs and my car cruises at 2200 RPMs that'd make up for the pulley. And for a $25 pulley which was only an extra 5 minutes of work when the alternator went on it was worth the 5 HP or whatever it gained.

 

[snb778 5,000+ posts]

wow.. im totally having a somewhat similar problem... VERY frusterating figuring out what it is

what kinda car do you have?

 

[KyleBechtold 5,000+ posts]

you alt might blow balls at idle?

 

[Proximity 10+ year member]

It's the alternator. It's supplying enough current at higher RPMs, but during idle it drops off. Having an underdrive pully will undoubtedly make it worse.

 

[shellfish 10+ year member]

well I'm sure you could gain more from taking all the stereo equipment out and

reducing the weight. I always say this to people that want a fast car and stereo.

But I'm just one off them people that thinks that a car should ether be fast

(for the track) or luxurious for commuting. Thats why i have a sport bike and a car.

BUT try replacing that pulley with a stock one and see.

 

[on1wheel01 10+ year member]

well where did you get ur ho alt? ebay i imagine. remember at idle they only make stock ratings and are stock ones rewound. and since you have a set of under drive pulleys your alt is not producing what it would with a normal pulley on there. so i bet this is your problem. also like said have the alt checked. so either deal with the problem and enjoy the extra powa or loose the pulley and fix ur voltage problem. which remember if you send clipped power to ur equip it can fry it. I myself try to get all the current I can. I dont try to go fast in a car. Thats what my sport bike is for. But hey it's ur car if you wanna try to go fast in it then good luck

 

[shellfish 10+ year member]

I dont try to go fast in a car. Thats what my sport bike is for. But hey it's ur car if you wanna try to go fast in it then good luck

meh copy cat! jp

cheers to a fellow rider

 

[on1wheel01 10+ year member]

lol i know you beat me to it had to refill the whiskey and coke glass. and cheers also ride safe man

 

[Sarthos 10+ year member]

It's a 93 Honda Accord.

It is advertised as putting out 80 amps at idle, although that's at 800 RPMs and my car idles closer to 600 RPMs. 80 amps is the max output on the stock alternator. And how could low current be the problem if I'm not even running the stereo or any amps at idle and it still does the same thing?

A fast car with no stereo isn't horribly fun, and a slow car with a stereo isn't either. Also having two vehicles means double the insurance money, definitely not fun.

It's hard to get country music to clip amplifiers, I'd have to crank the stereo to the max and that'd be no fun for my ears //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

But the high output doesn't offset the pulley? I was sorta afraid of that. I wonder where my old pulley has gone...