technogeeky

Hey folks.

I'm a little confused here. I recently installed a new stereo in my car and I'm having noise come from my alternator itself (at least, I assume that's where it's coming from).

I can't hear any feedback or conductive/inductive noise in my stereo itself - it sounds perfectl fine. But my alternator makes a whining noise when the engine is revved.

I am running a 500Wx1 RMS bridged amp on my subs and a 75Wx4 amp for my highs.

I don't have a cap installed.


I have been unable to find a direct correlation between my amps being on and my engine/alt whining, but it obviously started after the stereo install.

Would a cap fix this problem? Do I need a 2-farad for 800W RMS?

Thanks,
-Drew


Cliffs: My alternator itself makes noise - 2002 SE (there is no audible noise from my stereo). Do I need a cap? What's wrong?

technogeeky

If it helps:

I didn't do the under-the-hood wiring, but the front amp is under the passenger seat and the other amp is in the trunk. The power wire for both amps run seperately. The two amps are grounded to cleaned (shaved) ground points near the respective amps.

Would insufficient ground be a cause for the alternator itself making noise?

I haven't done any sort of 'hypergrounding' or whatever it's called.

machinehead

Things to check in this order:

1) Head Unit Ground.

2) Amp Grounds

3) Big 3 Upgrade

4) RCA's

djfrestyl

iTrader: (89)

I would check my RCA's before the big 3...

technogeeky

Just to make sure we're on the same page:

There is NO audible noise or whine from the stereo itself. I can hear noise from the ENGINE, but not the stereo.

The instructions you listed in my estimation will correct stereo noise, not actual noisy alternators.

clive

first you say there is a whine, then you tell us there is no audible noise or whine? Where would it be coming from, if it wasn't the stereo? Makes no sense.

If you really do have alternator whine coming through the speakers, then either it is on the power line or it is an earth problem. More precisely it is an EMC grounding and shielding 2-box problem of which exist hundreds of different reasons for electrical noise. Anyway you need to diagnose where it is getting in.

1. First try for the power line. Get an old mains transformer, dremel the winding off it, and wind, instead, a low-resistance iron choke using insulated 12G cable. As many turns as possible. Connect that in series with the power line to the amp that suffers from the noise.
Does the noise stop?
Yes: It's alternator commutation noise on the car's 12V bus and installing a cap might be one way to help that.
No: It's either getting in on the input or it is common-ground effect.

2. Test the signal input by unplugging it. Does the whine stop?
Yes: It's cable related.
No: It's common return problem (common-mode)

3. If it's common mode, it is because you are using multiple grounds.
In general ALL grounds should be returned to a common ground point. Called 'star' earthing. Read up on it.
And also: With screened cables used for signal, only ground one end of the screen! Otherwise you will set up earth loops.

djfrestyl

iTrader: (89)

With all due respect, clive, you need to ease up on the electrical jargon. The means by which you have been suggesting your solutions are yes, effective and certainly backed by knowledge, but they are not the most practical for the majority of the users on this forum, myself included.

Technogeeky, when you have whine, you need to get all points of grounding, including RCA's, HU ground, and amplifiers.

Are you SURE the whine is not coming out of your speakers?

technogeeky

Yes. I can turn the stereo all the way down and still hear it. I can disconnect the speakers and hear it. If I rig the turnon, I can even turn the headunit off and hear it.

I can usually hear it some AFTER turning off the headunit - it slowly fades away.

It's coming from my engine bay area.

technogeeky

It's coming from the (aparently) overloaded alternator. The reason could be improper grounding still, but it's not causing the stereo to sound bad.

If you read my post again, you'll see the magical words

from the stereo itself

That's entirely correct. The stereo doesn't make the noise I'm talking about.
I don't. I don't hear anything other than beautiful music.


If there is some grounding problem, I submit that the alternator may be overloaded becasue of it. I'm not entirely sure how alternators work, and I'm having trouble deciphering your electrical jargon despite my somewhat-educated background.

I am not lying to you people - it would do no good for me. My stereo works great. I can't, at any point, hear anything other than music in my stereo. If I turn the volume to 0, however, I can hear my alternator itself quite well.

djfrestyl

iTrader: (89)

Upgrade your big 3 and see where that takes you.

Good luck man...

machinehead

didn't I say that?

technogeeky

djfrestyl

iTrader: (89)

Lol sorry man. I got sidetracked by the post above, riddled with jargon.

Pearl96Max

iTrader: (151)

Do you have any aftermarket pullies? Hows the belt on your Alt? Bearings good?

clive

Well frankly, this thread is in the wrong area! This isn't to do with hifi. This is to do with car electrics and should be in the thread for your appropriate generation of car.
If the alternator itself is whining, then the bearings must be shot. I'd take it out and have the bearings replaced and at the same time, replace the field brushes, the two little graphite blocks on springs.