Early this year I added a new stereo, speakers and amp. All went great and sounded awesome. A few months ago I replaced the stock alternator with a 100amp unit to ensure enough output for the stereo, e-fan and driving lights.

Have just noticed an irritating alternator whine through the stereo that wasn't there before the alt. swap. Didn't seem to notice through the summer when driving with windows down and true dual exhaust. With cooler weather and the windows up you can definitely hear the whine.

I know there are power line filters available, just don't know exactly what to get and where to inject into the system. Obviously, there is the constant and switched power sources to the head unit along with the heavy line that goes to the amp.

Any help will be appreciated!

 

The best solution I have found, which for you it seems is an TFI through the charging system, would be route the head unit power and ground wires to the battery directly. Take them out of the loop completely. The switched 12V can still stay up front but it is best to run it to one of the terminals on the fuse panel, either ACC or IGN.

I would bet that once you do that the alternator whine won't be a problem.

Just to be sure though, double check all your speaker wire connections and make sure they are solid and nothing is touching metal.

 

Thanks for the quick reply Matt.

The amp power and ground are direct to the battery. The switched uses the stock radio line. I guess there is a possibility for the speaker wire to have rubbed or shorted but don't think that would result in a alternator whine that increases and decreases with rpms.

 

Refresh me, are you using an after market head unit or a stock replacement type? The amp being wired to the battery is already out of the loop, so I'm more interested in knowing how the head unit or radio is wired. If it is drawing it's power from the dash harness it could be picking up RFI from the charging system.

 

i had the same problem you did. a couple of these guys solved my problem. http://www.crutchfield.com/p_127SNI1...1.html?tp=1522

DB, i had all my stuff wired directly to the battery. stereo power/ground and amp power/ground. just the switched source and antenna were the only thing hooked up to the cars harness. i was getting terrible alternator whine from it.

 

If the RCA filters worked for you then your problem was never the power and ground wires. It was always the RCAs. They can pick up interference from any wire they run along or across. Just depends on quality of the shielding. The RCAs are likely still picking up the interference but the filters remove it before the amp.

 

the problem would have been inside the head unit then. i hooked my rcas upto a portable cd player and everything was fine.

 

DB, it is a JVC after market head unit with a 4 channel amp in the back.

Here's the thread from when I did the install back in March.
http://forums.corvetteforum.com/c3-g...done-pics.html

another-user, is that a ground wire on those filters? If so, am assuming that is need to be grounded out for the best result?

 

yes it is a ground wire. i threw the little instruction pack away long ago, but from what i remember it says to just plug the rcas in. if theres still a whine after that, then ground them out for further noise reduction.

 

One solution to that same problem I discovered by accident......I solved the problem by installing a new, larger capacity battery. I needed a new battery so I replaced my 700 CA battery with a 1000 CA battery. The larger grid (and better ground) of the new battery took away the whine.

 

Interesting... The battery is new (LT 10 months), so really would like to avoid that expense. Something to file away in the memory banks though. Thanks.

 

Thanks, I'll give them a try.
Crutchfield has some good stuff.

 

Okay I recall that thread. Where did you run the power and ground wires from the head unit? You said the switched source is the factory harness but what of the constant power and ground?

 

Without pulling the head unit I cannot say for certain (sucks getting old - memory is the 2nd thing to go right after..... uhh.. ).

What little memory that serves I believe/trust I would have tried to use the stock switched wire (yellow possibly?). Gnd, am not sure.

I know it is not antenna related as it also does it with the USB and Ipod connections, so it has to be in the power/speaker neg. lines.

 

if you pick up those noise filters, youll have to pull the head unit anyways. those guys go right to the back of the HU.

 

It might still be antenna related simply because some head units draw ground from the antenna as well. I have run across a few that don't work right i the antenna is not connected.

In order to rule in or out, the head unit power and ground wires...run jumper wires from the battery to the head unit, disconnecting the ones connecting to the stock harness. Should be easy to do by simply pulling the head unit out of the cage from the front giving you access to the head unit harness.

Connect the head unit power and ground wires to the battery with the jumper wires, and run the car and system and see if the interference is still present. Then we can move on to other possibilities.

 

Thanks all. Am ordering the filters and will also do the power/gnd wire testing also. Will post up the results when available.

Cheers!

 

what no one has really said here is what the problem is. The problem you are experiencing is a ground noise problem. The sound should get higher with the more revs of the engine.

usually its a bad component or a cheap component. from the sound of it you have decent equipment. So someone said to put filters on the RCA cables. The rcas CAN as said above pick up noise if ran along power and ground wires. that is why we always run the mon opposite sides of each other.

Good RCA cables such as street wires zero noise cables should elliminate your problem without the use of filters. Agood solution for you and one that may benefit you also is a capacitor. just a small 1/2 farad cap will filter out your line noise as wel as give you the benefits of a constsnt power source.

do you have the noise if you switch the blue wire (switched source) to a constant? if not ,then its coming in from one of the 30 year old components that you got the switched power from. wipers are not a good source and either is the HVAC contols,usually a horn is best!

one last problem you could have is just that! BAD GROUNDS. check em all. at the amp and the headunit. High end audio head units dont usually have the alternator whine, but,DO NOT GROUND directly to the battery. instant noise source. instead use the frame somewhere

cliff notes - re check grounds. make sure cables are not run over a power source. think bout adding a cap, and check your remote wire.

 

you didnt have the noise because the portable CD player was an islolated power suppply

 

After last evening, I believe there is a ground issue or the alternator is crapping out, but ground seems more the culprit.

We participated in a Christmas parade with our local club. Just before and during the parade I noticed that the alternator was dropping to minimal charge per the gauge, then it would kick back up to normal both at idle and higher rpms. The only draw was parking lights, stereo, heater fan and occasional e-fan cycles. During the summer this same setup easily powered stereo, headlights, driving lights, e-fan and AC. At idle it would pull down just a little below the 12/13 line on the gauge but immediately go above with minimal rpms.

The belt is tight so its not that.

When the gauge was showing good output, the whine was effectively non-existent, when the output dropped it would become much worse.

I do have the amp grounded to the battery and will change that to a different/frame ground.