Having trouble locating the alternator positive terminal?

Tiny
SWANBOMB4
  • MEMBER
  • 2008 CHEVROLET MALIBU
  • 66,000 MILES
Im upgrading my stereo system with the "big 3" upgrade and I need to connect 4gauge wire from the positive terminal on the alternator to the positive terminal on the battery. Do I have to move anything, or what is the best way to get to the positive terminal on the alternator?
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Saturday, February 18th, 2012 AT 12:19 AM

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Tiny
CARADIODOC
  • EXPERT
What are you trying to accomplish by adding a wire to the one already there? An AC generator is self-regulating as far as current output is concerned. You can't get more out of it than it is designed for.

Be aware too that you can not remove your existing radio. GM had a huge failure rate and to prevent people from buying high-quality replacement aftermarket radios, they started building the Body Computer into them. Got'cha. They do make radio relocation kits so you can put the old one in the trunk.
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Saturday, February 18th, 2012 AT 12:45 AM
Tiny
SWANBOMB4
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Ok, but I already have an aftermarker radio installed and is working fine and has been for a year now! You just needed a bracket and a wiring harness for the antenna signal. And about the alternator, im trying to accomplish "THE BIG 3 UPGRADE" it improves car audio sound tremendously by adding bigger gauge wires. So, with that said ALL I need to know is where is the positive terminal on the alternator is? And what is the best way to get to it?
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Saturday, February 18th, 2012 AT 3:31 AM
Tiny
CARADIODOC
  • EXPERT
I think you're being duped. The existing wire is plenty to handle any current the generator can produce. You would be better off using a slightly smaller wire to add just a tiny fuzz of resistance to the circuit. That will cause a very small voltage drop to occur. THAT is what you're trying to avoid by going to larger cables, and it makes sense, but if you read to the end, you'll see why a small voltage drop in that wire can save a lot of headaches.

If you need more than that to blow your ears out perhaps you should reconsider how rude the noise is going to sound to other people. Thank goodness they passed a law in my city that allows the cops to confiscate noise-making equipment after one warning. If you're going to play noise for the benefit of other people, at least play something that is pleasing to the ear and from someone who has at least an ounce of musical talent.

Anyhow, here's a photo from rockauto. Com that shows the output terminal. I had to guess which engine you have. This is for the 3.6L. The 2.2L generator is a little different. I added the two red arrows to point to the output terminal. It is always the fat wire and is always bolted on for a good electrical connection, ... Except on a few Ford models where the car designers weren't bright enough to understand what happens when high current goes through plug-in connectors.

If you're trying to reduce the voltage drop in the wire feeding an amp, that should come right off the battery but you really have the wrong brand of car to start with. GM insists on using side-terminal batteries that don't allow for connecting additional wires. You must absolutely never stuff any wires under those cable connections. Doing so will create more problems than if you use a dinky little wire going to the amp. You should have a fairly good-sized positive cable going to the under-hood fuse box. Bolt your new cable to the same nut the battery cable goes to.

Here's some other things to keep in mind. These are not sarcasm; these are facts. General Motors went from the world's second best generator to by far the worst pile ever starting with the '87 models. You absolutely do not want to do anything to assist it delivering its maximum current. Run your amp off the battery and let the generator recharge it at its own pace. This is not because something is going to overheat or anything like that. These generators use an internal "pulse-width-modulated" voltage regulator. That means to control it, the regulator switches the input field coil on and off about 400 times per second. The ratio of "on-time" to "off-time" changes depending on the needs of the car. Switching current on and off to ANY coil of wire is exactly the same as switching an ignition coil on and off. (It's why it is possible to feel a tiny zap when touching the terminals of a 12 volt relay when it turns off). When switched on, the electromagnetic field builds up relatively slowly because it takes energy to do that, but when it is switched off, that current flow has no choice but to stop instantly, and that makes the magnetic field collapse very fast and "induce" a voltage spike into the output winding. That is exactly what we want an ignition coil to do so it can develop enough voltage to fire a spark plug. We don't want generators doing that but GM's design is very effective at creating those spikes. The more current it tries to produce, the bigger those spikes will be. Those spikes will destroy that internal voltage regulator, can destroy the output diodes, and when there are spikes in the current flow through that output wire, they show up in the magnetic field around it too. That gets magnetically coupled into any other nearby wires, and if those are Engine Computer sensor wires, it will interfere with those sensor signals. That's why a lot of GM cars have stumbling and hesitation problems that clear up when the generator is disabled by unplugging the small connector.

It is already very common to go through four to six generators in the life of a GM car. One replacement is typical for an average car. The number one thing you can do to reduce the number of repeat failures is to replace the perfectly good battery at the same time that you replace the generator. Without going into all the theory, by the time the battery gets to be two or three years old, its "internal resistance" goes up. It will still crank the engine just fine but it loses its ability to dampen and absorb those voltage spikes. If you really want to know more about internal resistance, I have an entire page on my automotive electrical web site devoted to it, and another page all about your generator and the really nice older design.

Stuffing any wire or cable under the battery cable where it bolts to the side post battery adds to that internal resistance and will make it much more likely the voltage spikes will do some damage. GM even uses "zener diodes" in their output circuit but it doesn't solve the spike problem. Regular diodes are one-way valves for electrical current; nothing more. Zener diodes do the same thing, except in the reverse direction, they WILL let current flow once the reverse voltage has reached a designed-in value. The intent is to short out those spikes, but that only works when current is trying to flow backward. The diodes still have to let current flow forward to go to the car circuitry and battery, and the spikes are free to go along.

As I mentioned way at the beginning, if you add a small amount of resistance to the wire going from the generator to the battery, you will never notice the voltage drop with the 14.0 to 14.7 volts the system is developing because the percentage is so small, but when you start with a 30 to 60 volt spike, that resistance will cause a voltage drop that just might be enough to stop some damage from occurring. The battery will be less likely to absorb the spikes at the generator, (which could increase the chances of a damaged diode or regulator), but it will decrease the chances of some other computer on the car being damaged.

What you're trying to accomplish with these obnoxious amps is to eliminate any voltage drop in the cables supplying the current. If you understand Ohm's Law, it's not hard to see that you can easily have a one or two volt drop between the battery and the amp. Normal car radios and amplifiers have internal regulator circuitry to run the amplifier stages on around ten volts. That's why they still sound clear when the battery is running dead. Large amps need a higher voltage to allow them to develop higher output so many of them don't have those power supply regulator circuits. They run on the straight DC voltage coming in. It's the nauseating bass notes, the very low frequency notes, that require a lot of power, and a lot of input current. THOSE are the ones that need that large battery cable. When the current jumps up for those notes, that's when the voltage drops in the cables are going to a problem. If you start with, let's say 14.5 volts at the battery, and drop 2.0 volts in the cable, the amp is going to running on 12.5 volts. Once the bass note is over, current flow goes back down and so does that voltage drop. That means the voltage supplied to the amp goes back up to 14.5 volts. It's that change in voltage that can cause distortion in the output, but if you're listening to (c)rap, who can tell anyway?

There's a better way of solving the voltage drop problem. You can buy a special capacitor to attach to the supply cable right by the amp. Think of that as a balloon on the side of a garden hose. If you're getting pulses of water pressure from the water pump, the balloon will fill and empty in time with those pulses and tend to smooth the water pressure out. A capacitor is just like a very small battery in that respect. Even the "giant" capacitors marketed for what you're trying to do fall way short of their goal. One of them would not run all the circuitry on your car for one second. Your battery will do that for an hour or more. You can even pay extra for a capacitor with a digital voltmeter built in. Quite the gimmick but people fall for it all the time. Harbor Freight Tools has dandy little digital voltmeters on sale all the time for $4.99 that you can attach and even put inside the car where you can see it!

Instead of paying more for a capacitor than for a new car battery, a much more effective alternative is to buy a new battery for your car, then mount the old one in the trunk right next to the amp and wire it in there. It will hold the supply voltage steady, and instead of having pulsing voltage drops in the cable coming from the front, the current will tend to smooth out and be steady. The battery in back will take in current during the higher voltages and give it off during the bass notes much more effectively than any capacitor. That goes back to my story about internal resistance. A battery's internal resistance goes up as it ages and lead flakes off the plates, but it's still way less than the internal resistance of a capacitor.

You might also consider mounting a small garden tractor battery in the back. Just keep in mind that anything you do to modify any part of your car, lawyers and insurance investigators just love to find things like that. That includes any aftermarket radio or entertainment device, anything to do with the brakes, and especially anything to do with the suspension ride height.

Entertainment equipment suggests being entertained non-stop is more important than paying attention to your driving and the people around you. The world's worst lawyer will have no trouble convincing a jury you were partly at fault for the crash caused by the other guy running the red light if there is anything modified on the car. He will be right when he says the manufacturer spent hundreds of hours designing the brake, steering, and suspension systems to provide the best possible handling and control, and now your car has less than what it had originally. A battery mounted in the trunk can be crushed in a crash and spray acid, or it can short out and cause a fire. Young kids have enough stacked against them already when sitting in a courtroom. There's a lot of stuff you can do to modify a car that lawyers will use against you. This isn't a lecture. It's just my little legal disclaimer to help you be informed.

I'm very happy to hear you were able to remove the original radio. That is definitely not true on most GM products beginning with the 2002 model year and it makes me angry that a manufacturer would pull that kind of BS on their unsuspecting owners. Since they put the Body Computer inside the radio, removing it will leave you with no cruise control, no chime, no power windows, and since it's the master computer that tells all the other computers to turn on, the car won't run without it. There is absolutely no reason to design a car like that except to separate owners from their money after the sale. There's a reason GM is suddenly making a lot of money. They were having a hard time finding repeat customers, but they sold a lot of new cars during the cash-for-clunkers fiasco. They're going out-of-warranty now and those people are being hit with unbelievably high repair bills.
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Saturday, February 18th, 2012 AT 7:11 AM
Tiny
SWANBOMB4
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Ok I kind of understand most of that. I really do appreciate your help and input, but for one im not a "young kid" and I drive for a living and music is my life! I love all kinds of music not just "crap." With all do respect, just because I like my music loud doesn't mean im trying to be rude at all! I just like it loud n clean! My system is SQ not SPL, I just have top of the line equipment that runs alot of watts and it dims my headlights when my bass hits. I researched it and found that doing the "big 3 upgrade" will fix that problem and improve sound quality in the car. So, which exactly would u recommend? Putting a capacitor in by my amp? Or adding a battery? Im just trying to stop my headlights from diming and voltage drops.
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Saturday, February 18th, 2012 AT 7:41 AM
Tiny
CARADIODOC
  • EXPERT
Voltage drops aren't the problem if the head lights are dimming. They are on an entirely different circuit that draws very little current. The only way for the voltage to be low there is if what's supplying that voltage can't keep up with the current, (amps), demands. A different way of saying it is you could eliminate all the potential voltage drops with giant cables, but the amp is already drawing enough current to pull the battery voltage down, as seen by the head lights, and you want it to be able to draw even more. If voltage drops in the cable feeding just the amp were the problem, the battery voltage would stay up and the head lights would stay bright.

The exception would be if the voltage drop is occurring in the positive cable between the battery and fuse box or the negative cable between the battery and body. That negative cable to the body is usually pretty thin but it has to handle the same amount of current as the positive one. I think I'd look at that one first as the likely weak link in the chain. Head light current has to go through it too so it will be affected by its voltage drop.

By the way, do you know how to TEST for voltage drops? Finding them and correcting them might be faster than just running lots of cables. You'll need an inexpensive digital voltmeter. The only place you can't test is where the cables attach to the battery unless you have a replacement battery with the dual posts on top and side posts.

Upgrading the wire from the generator to the battery isn't going to help because what GM gave you is sufficient to handle the 120 to 150 amps it is capable of. It's up to the battery to be able to supply the needs of the entire car, current-wise. The generator just keeps the battery charged as it sends its current to the car.

Before we go any further, I'd like to know exactly what you have for voltage right at the amp with the volume turned down and with it up high, and what you have at the battery, same two conditions, all taken with the engine off and with it running. If you do find the voltage is dropping on bass notes at the amp more than at the battery, I'd try adding a battery right by the amp. Its voltage will also be drawn down on bass notes but not nearly as much as the main battery's voltage. Nothing in the rest of the car is going to draw high pulses of current so if the head lights still dim with a battery by the amp, you aren't going to solve it without adding many batteries.
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Saturday, February 18th, 2012 AT 10:23 AM
Tiny
SWANBOMB4
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Ok now I understand. I do not unfortunately have a voltmeter at this time, I could get one some time this weekend to test the voltage. But I think from listening to what you said about the negative to body ground wire being thin and still having to handle the same current is where the problem is and I agree. I checked and both grounds to the body and engine block are both thin, so upgrading those 2 or even just the body ground would suffice, correct?
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Saturday, February 18th, 2012 AT 10:50 AM
Tiny
SWANBOMB4
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Ok, so I added 4awg ground wire to the body and I already notice a difference in the sound quality! Its not dark outside so I wont know if it solved the dimming problem until it gets dark, but I do notice a change in the sound quality. It sounds better already, so thank you very much for the help and saving me time and money!
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Saturday, February 18th, 2012 AT 7:34 PM

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