My radio is dimming my lights when the bass hits

Tiny
CHIZUK25
  • MEMBER
  • 2006 CADILLAC CTS
  • 47,000 MILES
I have a 1000 watt amp running my stereo system and my lights are dimming. My battery is a 650cca and still strong. My alternator is a 95 amp. Which the replacments they have 105 and 110. How or what can I do to stop the lights from dimming when the bass Thanks a million
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Saturday, October 15th, 2011 AT 8:21 PM

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Tiny
CHIZUK25
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HOW do I stop the dimming of the lights
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Saturday, October 15th, 2011 AT 8:53 PM
Tiny
CARADIODOC
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Maybe you don't get the answer you want because you don't include any details. You think we're psychic and we're going to figure it out. Instead, we have to ask, and ask, and drag the information out of you like it's some kind of secret. Why on earth would you refuse to add details?

Do the lights pulsate up and down all the time or just when the amp is turned up high? Do they stay constantly dim or do they pulsate / flicker? Who installed the system? Did the problem occur right away or did it start acting up days, weeks, or months later? Did the lights dim BEFORE the system was installed? What have you checked or tried so far? If I'm supposed to take into account every variable of every possibility that can cause a complaint of "lights dim", I don't have that kind of time left in my life! My fingerprints won't hold up that long from typing.

As for those donations, thank you to those of you who do donate. It makes it worthwhile sitting here all day and researching in service manuals, but the fact is, we don't know who donated and who didn't. We're volunteers who earn a tiny compensation for the effort we put in trying to help people with legitimate problems. I spend just as much time on every question that I think I can help with without knowing if you made a donation.

You're right about my remark too. Loud stereos are only used by children who think they're going to impress people with a car that sounds like a dump truck rumbling down the highway. Every teacher knows peoples' brains aren't fully developed until their mid to late '20s. The decision-making part is one of the last to develop and it's why youngsters such as yourself make many lousy decisions and fail to understand the consequences of those decisions. Likewise, they aren't begging for attention by doing stupid things like face piercings, and playing their "music" for people blocks away. The rest of us who have grown up are not impressed with your childish behavior. You have to remember, we were once your age too and we now look back on the things we did and shudder at how stupid we were. Unfortunately for you, we can't teach experience, we can only tell you about ours and try to explain what's going to happen later. We're telling you you're going to suffer hearing loss later in life because we know. It has happened to us at a time when there's lots of things and people around us we wish we could hear. Every year in my auto shop I made my students wear an eye patch for a day to point out how important it was to wear safety glasses. I suggest you get a set of ear plugs and wear them non-stop for a day to understand what every day is going to be like when you get older. Running around with a hearing aid dangling from your ear isn't cool.

I can't believe some of the things I did years ago, but I can sure recognize them now when other people do the same kinds of things. You have plenty of time left in your life to earn respectable attention. There's no need to show off in hopes of getting people to notice you now.

So keep in mind we hate your loud stereos that interfere with our enjoyment of life, but I'll still try to explain why you're having problems.

To start with, there's no way to sugar-coat it, General Motors has had by far the world's worst pile for a generator since the 1987 model year, and they have no plans on changing it, especially since it's one of the many ways they've figured out to separate you from your money. Due to their design, they develop a lot of huge voltage spikes. Those spikes can destroy the internal diodes and voltage regulator, which is the main reason for repeat generator failures, and those spikes interfere with computer sensor signals. Your car is full of unnecessary, complicated, unreliable computers to do things that computers were never needed for before. (That's not just a GM thing; that's true of all car manufacturers, and is the main reason mechanics won't buy newer cars). To reduce those repeat generator failures, the perfectly good battery must be replaced. As they age and the lead flakes off the plates, they lose their ability to dampen and absorb those spikes. The old battery will work fine in a 1986 or older car.

The voltage spikes also confuse the computers on your car. They require a smooth steady voltage supply. When that voltage drops sufficiently or when it varies rapidly, anything controlled by a computer can do weird things. That includes power windows, power locks, computer-controlled transmissions, heater / AC controllers, instrument clusters, ... And head lights. It's also a real common cause of unusual engine performance problems, particularly at specific speeds and / or loads.

The next problem is your battery is too small electrically. About the only way to get a 650cca battery is new with the car from the manufacturer. Replacement ones that small are out there, but it takes so little to build a bigger one that they can charge more for that almost every replacement you find will be closer to 850cca. Years ago that would have been double what came in most cars, but back then the only consideration was having enough current capacity to crank the engine on a cold morning. Today the battery is the main component in helping the voltage regulator do its thing. It also has to fill in for the generator when it can't keep up to your amp.

You'll need to look at the battery cables too and where you attached the wire feeding the amp. GM still insists on using the troublesome side post battery terminals. Many do-it-yourselfers lift the positive cable and stuff extra wires under it. To work properly, those cable ends have to be fully seated squarely on the battery. By adding wires, it is still possible to get enough current through to crank the engine but there will be a tiny amount of resistance added to the circuit. When the battery has to make up for what the generator can't supply, that resistance becomes important. Current flowing through a resistance causes a "voltage drop". That in itself can lower system voltage which can be seen as head lights dimming. When those battery cables don't sit flat against the battery, moisture will find its way in there and form corrosion over time. That will cause increased resistance and a gradually increasing problem with system voltage. That's where knowing when the problem first acted up is a helpful clue. If the problem started a couple of months after the system was installed, it got gradually worse, and there's wires stuck under the battery cable, the diagnosis is pretty straight forward.

With a very small amount of resistance in the battery cable connections, it will look to the voltage regulator like the battery is fully charged when really it isn't. The regulator senses system voltage, not battery voltage. They're supposed to be the same thing but that resistance in the cable connections isolates the battery from system voltage. When the regulator sees system voltage increasing over a fraction of a second, it tries to cut back on generator output, but it can't cut it back far enough. System voltage keeps rising until the regulator takes drastic measures to stop the increase, then system voltage drops, the regulator kicks back in to turn the generator back on, and the process starts all over. That is avoided by having clean, solidly connected battery cables.

Head lights, and the rest of the stuff on the car, use less current than the starter so the wires feeding all of those circuits are smaller in diameter. If you attached your amp feed wire to one of those circuits, it may be drawing its current through some of the same wires that feed the head lights and other circuits. Every wire has some resistance, and the smaller the wires, the higher the resistance. That means more voltage will be dropped when the amp draws high current for the bass notes.

If you look at your under-hood fuse box, you will likely see a smaller positive battery cable bolted to it. That is probably the best place to add the feed wire for the amp. It's close to the battery without compromising the battery cable connection, and it avoids drawing current through the wires that feed the rest of the car.

Your amp does not produce 1000 watts all the time. That is the most it will produce during the bass notes. If you do the math, according to Ohm's Law, current equal power divided by volts. 1000 watts divided by 12 volts equals 83.3 amps. Your generator might be capable of more, but 90 amp generators are fairly common today. It takes about 10 amps to run the fuel pump, 10 amps to run the ignition system and injectors, 10 amps to run the irritating daytime running lamps on high beam at 80 percent of normal brightness, (that requires a computer), and another 10 amps to run the heater controller and all the other computers. That leaves 50 amps to run the radiator fan, power windows, wipers, and brake lights, with just a little left over to recharge the battery. Now add in an amplifier that draws half as much as the starter motor and you can see that you'll be taking current from the battery instead of putting it in to keep it charged. 83 amps to the amp is the peak. It doesn't draw that much all the time, but it's when it does that the electrical system can't keep up.

To sum it up, there's a number of things working against you leading to dimming lights. You have an extremely poorly designed generator by a manufacturer that has no plans to improve it, you're adding a very high-current accessory the electrical system wasn't designed to handle, you have a battery that's too small electrically, with side-post terminals that already limit how much current they can handle, and it may not be getting fully charged, you have a lot of computers that respond adversely to the resulting fluctuations in system voltage, and you may be taxing other electrical circuits depending on where the feed wire is attached.

After you've addressed all of those concerns, if the problem still exists, you might consider performing a series of voltage drop tests to see if any high-resistance points can be located and corrected. Voltage drop measurements are typically only used
in high-current circuits like starter circuits, but they are effective in any high-current circuit. Rather than measuring the voltage AT various points in a circuit, you're measuring very slight differences in voltage BETWEEN two points in the same circuit. That eliminates the variable of momentarily dropping system voltage that would skew the readings. If it comes to that, I can post a copy of the description I typed up on how to perform voltage drop tests. It really pertains to starter circuits but the procedure works in any high-current circuit.
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Saturday, October 15th, 2011 AT 11:16 PM

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