Alternator whine.... need some opinions..

[HillBilly]

Well, I have one hell of an alternator whine in my mercedes.

Here is what I have done so far.
Remove the factory head unit. Wire a Metra harness to the new head unit harness. (to keep the factory wiring harness) Re-arrange pins in the metra harness as required. Install the new head unit, utilizing the factory Bose amp and speakers.

so now is where the alternator whine shows up...

It is almost gone with the engine off, but with the engine running, it is VERY loud.

To diagnose the probelm, I have done the following.

Ran a ground wire from the deck to the battery neg terminal. Still there.

Separated the RCA's and the power lines as far as I could. Still there.

Remove the radio antenna. Still there

Unplug all the RCA's while the unit is running... Sound is gone.


looking for ideas.....:banghead:

[97'Scort]

It's from the deck power supply. BMW and Mercedes cars are horrible for this: the power wire for your deck runs through just about everything else in your dash and the power is very dirty once it actually gets to your system.

What you need to do is run a new power wire straight from the battery, and pick up a power choke:

http://www.scosche.com/products/sfID1/151/sfID2/156/productID/1095

And that should do it for you.

[HillBilly]

I tried running a dedicated power, and ground from the battery. Same result.....

Do the power line filters actually work? Am I just wasting money on something that probably won't work?

[ShermanEF9]

check your grounds. when mine wasn't in correctly i was getting one hell of a noise.

[97'Scort]

Originally posted by HillBilly
I tried running a dedicated power, and ground from the battery. Same result.....

Do the power line filters actually work? Am I just wasting money on something that probably won't work?

Worked for me. I had whine in my system from day one and I eliminated every other possibility. Put in the filter and it worked perfectly.

It's not exactly small, though, so you'll probably have to find somewhere to put it behind the glove box or something.

There are a couple more things you can do to check if you're unsure:

1. Grab an iPod (or discman, or whatever) and a 1/8" to RCA cord (headphone to rca). Unhook the rca's from your amp and plug in the iPod. If you still have whine, then it's not a result of your head unit, it's power/ground, or anything to do with the RCA cables in your car. If the whine is gone, then it's a problem with the head unit or cabling thereof.

2. Grab another length of RCA cables, and disconnect your RCA's from your system entirely. Plug in the new set, but simply run it through the car and into the trunk to the amp, (no installing, just run it over the seats, you get the idea). If the whine is gone, then the RCA's are the problem. Shielding does bupkis in RCA cables, so if they're at fault, get a high end TIGHT TWIST set. The twisting creates opposing electric fields that helps eliminate radiated noise.

If the whine is still there, then it's your head unit.

This test can also be done with the iPod and a couple of female-to-female RCA adaptor plugs and your existing installed cable.

3. You've run a new ground for your head unit, I'm assuming to an unpainted metal surface. The only thing left is the power coming in, and if you've already run a new fused connection (with the fuse <14" from the battery) then the filter is your next logical step. For $15 you can't really go wrong.

Edit: Also, never run your ground straight to the battery. Ground to the chassis.

[///LOUD LOAD\\\]

Ground your RCAs out on the back of your head unit.

[97'Scort]

Originally posted by ///LOUD LOAD\\\
Ground your RCAs out on the back of your head unit.
I always hear people say this...but I've always found the problem to be elsewhere. I don't see why it should work anyways: the RCA's should also ground at the amp. So unless both your amp and your HU RCA grounds were absolute junk, I don't see how it would improve the problem.

[///LOUD LOAD\\\]

Originally posted by 97'Scort

I always hear people say this...but I've always found the problem to be elsewhere. I don't see why it should work anyways: the RCA's should also ground at the amp. So unless both your amp and your HU RCA grounds were absolute junk, I don't see how it would improve the problem.

Well in most cases its the deck that has the bad ground connection for the rcas, not the rca or the amp. Pioneer is well known for this problem. I run pioneer and i have always done this with every one of my head units.
If you ground the RCA out at the amp side just watch your sub jump!!! lol
But this is such a simple fix and takes all of a few minutes to check if it helps or not so why not try it.

[97'Scort]

I run pioneer too, and the power line filter cured my whine problem. You probably remember my "whine pt I and II" threads over at CCA.

[///LOUD LOAD\\\]

No i dont pay much attention to what goes on over on cca besides laughing at how easily the east can be talked into believing complete bs. haha

[HillBilly]

Ok boys... some new info.....

last night i hooked up the deck and used an mp3 player for sound.. Well, she is dead quiet... no noise at all.. If I plug the RCA's from the deck, the whine is back..

here is the really weird thing... With the deck hooked up normally;

With the key at position 1, the sound is clean
With the key at position 2 , the sound is dirty
With the engine running, the sound is dirty

WTF??? :banghead: With the key at pos 2, the altenator isn't turning, so it can't be altenator noise.

I have a power line filter on its way here....

[///LOUD LOAD\\\]

Originally posted by ///LOUD LOAD\\\
Ground your RCAs out on the back of your head unit.

[em2ab]

I had the same problem as your initial problem, as well as your new problem.

The initial problem I solved by getting a ground loop isolator from Radio Shack for $20:

http://www.thg.ru/howto/car_pc/images/carpc_ground_loop_isolator.jpg

As for your new problem, I got the same thing eventually, turns out my amplifier was actually grounding on my RCA so the amplifier wouldn't even come on if I didn't have the proper RCA plugged in. I just moved the ground point for the amplifier to a different bolt and problem solved.

[HillBilly]

Originally posted by ///LOUD LOAD\\\


not possible.. I'm using the factory wiring, which doesn't have a ground wire running between the RCA's like aftermarket cables do.

[97'Scort]

Originally posted by HillBilly


not possible.. I'm using the factory wiring, which doesn't have a ground wire running between the RCA's like aftermarket cables do.

What he means is you actually solder a piece of wire to the outer part of the RCA connector, then directly to your head unit chassis, for both left and right.

[HillBilly]

Well, i tried the power line filter today.. same shit.:(

I have pretty much scraped the whole thing until spring. Once it warms up, I will try again. Any ides for then?