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is there any way to just fix the alternator whine?

9259 Views 10 Replies 7 Participants Last post by  Arch
The setup: 2007 Mazda3 with the auxilary input.

The problem: Alternator whine when ipod is plugged in to AUX jack with the power plugged into the cigarette lighter inside the center console.

Current solution: Ground loop isolator.

My beef with this: The only cars that i have ever seen with ground loop problems are older cars with poorly installed stereos.

Isn't there some way to fix the ground loop (such as grounding what needs grounding) rather than just put in a stopgap such as a ground loop isolator?
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Could you be hearing transformer noise instead from whatever you have plugged into the cigarette lighter, or does it really vary with engine speed?

If you have something plugged into the cigarette lighter, it could be modulating the DC quite a bit if it had a poor quality DC-to-DC voltage converter.
no... it definitely changes with the engine speed.

the exact setup worked fine in my wife's 96 nissan altima with a head unit i installed myself.
Ground loop isolators only filter the noise. Sounds like the center console power plug has a poor ground.

Does it happen when you plug into the cigarette lighter (dash) for a power source?
yes... it happens on both the center console and the dashboard power plugs.
If it were mine, I'd isolate where the noise is being injected. Run a cord from the battery to your power adapter, see if the whine stops. If so, you have a power problem, & can run new power leads to the center console from the battery. If not, then the input jack wiring has problems, & the leads from the radio to the jack need to be shielded (replaced with better cable) or re-routed.
does the ground loop isolator do the trick? if so, be happy with it. what would fix the problem ? components with better isolation, and or an isolated power supply!
Hi. I also have the same problem with my Mazdaspeed 3 and I took my car in to my dealership to see if there is anything they can do to fix this. I was told by my dealership that the buzzing/hum that changes with acceleration was within there normal specs. I was like WTF. I then started looking up options as you are to solve this problem for my Sirius Satellite radio. Well because I live in Toronto and the PAC SNI-1/3.5 Noise Filter is not available here by any Ontario PAC supplier so I bought it off ebay and it just arrived today and I can tell you for sure that it gets rid of all that noise problems and preserves the sound without changing the volume. So I would recomend getting it, it is quick and does not need any extra skills to install other than plugging it in.

I hope this helps!



Crutchfield ground loop isolator. 18 bucks, plug it in, problem solved. Works perfectly...
alternator whine is cause by a ground loop. hence the need for a ground loop eliminator. What is a ground loop? well a ground loop is formed when devices are connected to ground in different places and a current flows throught the ground and through the devices.

So, for example our stereo and ipod problem. Our car stereos are grounded through the wiring harness. where that harness is grounded, god only knows. But lets say the ground wire runs all the way back to the battery. now then we plug in our ipods to the cig lighter socket and it has its own ground that may just ground to the metal body near the socket. then when you connect the ipod to the stereo a loop is created and current may flow through the loop.

current can flow through the ground from any point. lets just pick a spot to start and follow it. the ground path goes from the ipod to the stereo through the audio cables, from the stereo to the battery, from the battery to the cars chassis, through the cars chassis to the cig lighter, from the cig lighter back to the ipod and around again.

If you were to put a meter between the battery grounding point and the cars metal chassis where the cig lighter could be grounded. you will see that there is a certain amount of resistance between the two. and that the "potential" is different as well. IE meaning there is some voltage difference between these spots. adding other devices to the grounding system in the car makes the problem worse as each device imparts its own noise onto the ground. this noise then adds to the ground loop currents and increases the noise we hear.

people always assume that ground is always at 0 volts and in actuality it may not be. it depends on what points you measure and the potential of difference between those spots.

For example. lets say we take 100' of 2 conductor wire and at one end we twist the wires together and call that ground. At the other end of the wire we take the two conductors and connect each one to a 9V battery. one wire there we will call ground as well. (Do not try this at home kids.)

Now if we measure between each of the two conductors along the entire path from the point where the wires are twisted, to the point where the battery is connected. we will see that that as we get closer to the battery the voltage will increase from zero to some defined point. How is this possible? Well every electrical conductor has resistance. and due to the wires resistance some electricity is used along the way. and it is due to this resistance that we start to see a difference in potential the closer we get to the battery. this potential of difference is what cause a current to flow through the wires. In fact using ohms law, we can actually calculate how much current is flowing throught the wire in a number of ways. i wont bother you with those details here.

Now then. lets say one of those wires is a metal plate like our cars chassis. this has an extremely low resistance from one end of the plate to the other.

Now lets connect a wire with a higher resistance to the plate at one end. and we are going to connect our batteries neg terminal at that point as well. then lets connect another wire to the + terminal of our battery. we are then going to run our + and - wires to the other end of the plate.

If we take our meter, and connect it between the positive wire and the metal plate we will get one reading. and if we connect our meter between the + wire and the -wire we will get a reading that is less then the reading measured from the plate to the + wire. our new reading will be the same voltage minus the voltage lost due to the reistance in the wire. and if we connect a device between the + and - wires at that point and then measure between the negitave wire and the metal plate we will see a potential of difference between the two.

Now we get a bit more complicated. let say our car stereo is connected between the + and - wires and our ipod is connected between the + and the metal plate. each on there own will work just fine. If we connect a meter from the metal body of the ipod (assuming it is grounded internally) and the metal body of our radio's, we will see a potential of difference between these two. Not a big deal until you connect the ipod to your radio and then a current will flow through that audio cable because of the difference is potential we just measured. that current that is flowing is very noisey, it contains all of the cars electrical noise plus more and that noise then causes the ground point in the radio or the ipod to fluctuate slightly. that fluctuation then induces noise into our audio signal as ground is no longer constant. this is bad and this is why we hear alternator whine. fan motor noise, xenon ballast noice. injector noise, ECU computer noise etc etc etc. a cars electrical system is one noisey son of a b*tch!and every device that is grounded in a different spot creates is own ground induced noise.

ideally all grounds should be conneted to one grounding point in a star ground configuration. this is not always possible.

You could fix the ground loop by connecting the cig lighter ground to the same point where your car stereo is grounded. this would eliminate the ground loop. In fact, if you ONLY plan on using your cig lighter socket for your ipod, you could connect the ground of the socket directly to the car stereo chassis. But remember, you can then only use you cig lighter for your ipod, any heavy current demanding devices like a cig lighter will then require the stereos ground to then handle all that current as well as the radios current and it was not designed to do so and could fry. an ipod draws very very little current so you can do this safley as the ground wire will easily handle the tiny amount of current required by the ipod. Then as long as your ipod doesnt touch anything else that is connected to the cars grounding system, you wont have any noise.

keep in mind here that the voltages we are talking about could be very very small and you may not be able to observe them with your meter. but they are there and they are very real.

I hope i havent totally confused you.

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Most excellent tutorial, ZC!
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