Alternator whine
 

I've been finishing up my audio setup, and I've noticed I'm getting bad alternator whine.

I've gone the trick where you cross the RCA's at the 90's.

Do you think that the power wire (4 gauge) is too close to them? That wire runs pretty much parallel to the RCA's most of the way down the truck.

Let me know what you guys think, this afternoon we're gonna move the power wire to see if that helps.

Also I read somewhere that the radio's ground may not be good enough.

I would always reground my radio no matter what, whether you be replacing with aftermarket, or have your stock one out for a few, and have the time to make a new ground. I dont know if that would cause the whine, but I know the ground is terrible.

That's a good suggestion. Should I just cut the ground wire behind the radio then solder on a new ground?

well, first I'd find a good place that you can put a new ground, i.e. frame, cab, etc. then drill a hole so you can get a nut and bolt through it. this is also key when choosing the place. you want somewhere you can get the nut on the back. then, I'd get a little bigger wire, run it to the back of your head unit, and connect that with the thinner ground wire out of the the harness. make sure the connection between the two is good. and that where your grounding at, is sanded of paint, rust, etc.

There's a metal brace behind the dash that works perfect for a ground.

I dont know if it would be the best suggestion, but that works. I would just rather have it on the firewall somewhere or frame somewhere. somewhere where stuff isn't always touching it and interfering.

Nothing will touch it back there. If you have your wires half-way neat back there then it will be fine.

I think I know what metal brace you are talking about. I'll get to work on that this afternoon

well, all I can say is you can try different places. I almost fried my new headunit when I put it in, because my ground wasn't connected very good to the wiring harness. and lets just say mine isn't the neatest back there because I have all the plugs for my subs, my xbox, dvd player, nav input/output, bluetooth, ipod cable, etc lol. so I just ran a thicker wire down to the bottom of the cab.

Try to disconnect the rcas from the amplifier, if the noise is still there your probably picking it up through the amps ground location, if the noise is only present when the rcas are connected its most likely just a set of cables with a not so great shielding or the radio itself could be introducing the noise, id check both and try to eliminate each possible area, try with a set of nice well shielded rcas just over the seats just to test and see if it follows the cables.

what kind of HU do u have?

Kenwood KDC-794

How would the speakers still make the noise with the RCA's disconnected?

I think he thought that you had speakers wired to the head unit still, and not with an amp. lol. maybe not, but thats the only thing I can see.

It's always a good idea to run the RCA's as far away from power as possible. And at 90* to any other wires they come in contact with. You want to keep the crossing/overlapping areas as short as you can to eliminate EMF.

I have my power cable (1/0ga) running down the driver's side & my RCA's running down the pass side.
My old head unit has a hint of whine that I can only hear when I have the stereo muted, but it's not noticeable at any volume level.

I'm going to be installing my new head unit today & I'll probably add a filter to the head unit's power just in case the new one gets any interference.

Grounding the head unit away from the OEM wiring harness isn't a bad idea either. All the wires in there can easily pick up noise.
Just sand down any area you plan on bolting the ground wire to for the best connection possible. Wouldn't hurt to route the head unit's power away from any other wiring if possible.

ok cause i heard that pioneer sometimes will cause alt whine, just checking to see if that is what it was but u dont have pioneer.

this

Alright, so I'll go ahead and run a new ground for the headunit.

Then I'll move the power wire as far away from the RCA's as possible

Iv had customers in the past that have had amplifiers have noise without any audio signal going into them, if you disconnect them and theres still a noise present, most likely the amplifier has a problem internally or its somehow picking up ground noise from somewhere else, if you disconnect them and the noise goes away its just a way to eliminate a problem with the amp itself.

The problem has been intermitten, every time we move wires it does it louder or softer

Could you possibly narrow it down to which wires cause the noise flux?

I bet we could, when he gets off work we'll take the seat out and try different ones

my power and rca's run with each other along my drivers side, and they part ways at the firewall, and I dont have any problems :P so its probably the rca's.

Turns out it was the RCA's interfering with the front right speaker. When I pulled the RCA's away from that speaker wire it went away.

But I did go ahead and move the power wire away from the RCA's just to be sure.

Thanks for the tip, I will probably still end up regrounding the headunit though

Would it be possible to ground the HU and AMP to the same location? That way there's no potential difference between the 2 sources??

I wouldn't bother running the ground wire too far from the amp. I found a bolt close to my sub box and grounded it there.

Listen to Buggman everyone. Here's a tip: Never run the power wires and the speaker wires (sound and RCAs) on the same side of the vehicle. While checking the different components (amp, unit, speakers), ground, and everything is a good idea. If you run the power wires along wires that provide sound, you're asking for issues.