Here we go…

Several years ago, I bought a “hideaway” stereo system. It’s a SecretAudio system made by Custom Autosound. The system consists of the main unit mounted behind the dash out of view, a small screen that hangs under the dash, and a 6 cd changer which I have mounted under the driver seat. Four new Alpine speakers in the stock locations and new speaker wires.

Ever since this was installed, I could hear a whine that followed the rpm of the engine (somewhat like what you can hear on AM stations sometimes, except this was all the time either on FM or while playing a cd) I went back to the place that installed the stereo with the problem and they sold me a noise filter to install on the power wire going into the stereo. While installing it I noticed that the stereo already had it’s own noise filter, but I installed the extra one anyway… it made no difference. The “whine” was noticeable, but also tolerable, so I just let it go for all this time.

Recently I bought a Sirius satellite radio system: http://www.radioshack.com/product/index ... age=family (on sale for $79 plus I had a $25 gift certificate ) it just plugs in the cigarette lighter and broadcasts on a certain frequency, so you can tune your radio to that channel and hear it. I bought an extra antenna, so I can use it in my car or my truck easily. It sounds great in my truck, but in my car the same engine RPM whine I’ve heard for years has shown up about 5X louder than before. I can listen to the regular radio or a cd fine with minimal interference, but when I turn that Sirius unit on, my “audible tachometer” gets in the way so bad I can barely stand it.

I’ve read that this noise can be caused by a bad ground…. (here’s the kicker) I crawled under my dash and disconnected the ground wire that goes to the main stereo unit under the dash. My intentions were to run a ground wire straight from the main stereo unit to the battery to see if it sounded any different than using the stock ground under the dash. Just for the heck of it I turned the ignition on, not expecting the stereo to turn on… but it did . Now I’m by no means a stereo or electronics expert, but how it can work with no ground baffles me.

I’m kind of dumfounded as to why the stereo can work at all with the ground wire disconnected. It’s the only black wire coming out of the unit, and it’s labeled GND so I’m reasonably sure that it is in fact the ground. It also occurred to me that the case may be grounded by where it is mounted under the dash, I completely disconnected it and set it on a rubber floor mat… still worked. Just for kicks, I ran the ground wire to the battery, but it made no difference in the sound.

In order to reduce the much louder whine I hear while using the Sirius unit, I thought I might try installing my extra noise filter I have on the cigarette lighter power wires, but it seems as though I have some other underlying problem here. I’ve heard people say that this “whine” is produced by the alternator, is that true? If so, would a more modern alternator be designed not to produce this interference?

Thanks in advance for any info

hello, you may want to change your spark plug wires, a poor quality wire or a damaged wire will cause that, also try your condensor for your points and the condensor mounted on your voltage regulator, i would replace my wires first. good luck.

Thanks for your reply.. the spark plug wires are only a couple years old, and the problem existed before and after I replaced them. I usually change the points and condensor in the distributor once a year as a percaution.... I've never changed the condensor on the voltage regulator, I'll have to look arount to see what I can find.

Also, in my service manual, there is a 2 piece "shield" under the distributor cap. My car does not have that... maybe because it only had an AM radio from the factory? Just a shot in the dark.

The 3 things that can cause EMI (Electro Magnetic Interference) are your distributor, your alternator and the plug wires. I'm guessing since you probably have an externally regualted alternator, and you have done everything else, that the condenser here might be your problem. If you are ambitious, you could change over to a internally regulated alternator, like a Delco 10si or 12si. Should be a drop in replacement with a few minor modifications.

Also, what type of plug wires are you using? Solid core wires will emit alot more EMI than spiral wound or carbon centers.

Andrew

73delta, the stereo stayed on without the ground wire, because the casing of the stereo is metal. It is likely mounted to in some way, a metal bracket inside your dash. This is where it would be getting a ground to work with.

Do you have any other electronics or aftermarket equipment installed in the car?

How is the ground from the frame to the engine? And from the alternator to the frame/engine? Check out your distributor (coil), it needs a ground also. There are lots of grounds that could have an effect on your setup. Make sure they're all tight and un-corroded.

That shouldn't happen! ........ right? I'm going to try again and trace some wires around, hopefully I missed something.

I looked at my spark plug wires and the words "Radio Supression Core" is printed on them, not sure if it's solid, spiral, or carbon.

I'm thinking my alternator is internally regulated, this is from my wiring diagram:

Internal Tranzistorized Regulator

you can see my whole diagram here: http://www.oldsconnection.com/forum/tec ... elta88.php

more to come...

Sorry, didnt see the part where you set the radio on a rubber mat. There has got to be a ground on something. Unplug the coaxial antenna wire and see if it still runs. Something has to be making that circuit complete.

yea, I just figured that out and rushed back inside to post that it was grounding through the antenna wire.

ok, now the mystery of the ground has been taken care of... back to the audible tachometer.

Whine is alternater. Buzz is ignition.


Either put the filter on the alternator or run the power directly from the battery.

Norm

Yep, alternator whine and radio was grounded through antenna.....guess I'm a little late...

TOC Admin
Brando

Ran a ground wire from the ground on the radio straight to the battery and left the antenna disconnected. No noticeable whine. If I connect the antenna the ol' whine comes back loud and clear.

Tried Norm's suggestion and ran a positive wire straight to the battery as well, same situation. Once I plug that antenna in the whine comes back.

As for connecting the filter straight to the alternator, my filter was not intended for that type of installation, the one I have is only meant to filter enough power for an average radio, not the whole car. Maybe such filters do exist, not sure.