Dunasso

Over the past few weeks, I've noticed a constant whistling noise when I turn on the radio. It only does it when the engine is running and the pitch gets higher the faster I go. Does anyone know what causes this?

Duncan

RSAErick

I've heard that this symptom is often due to a poor ground.... but I have no electrical background, so take it with a grain of salt. Good luck though.

Bill Wagner

RSAErick is right....noise from the electronic control circuitry and/or the ignition system is getting into the supply leads of the radio and coupling right into the receiver circuitry. This is usually caused by bad grounds or bad shielding. If checking/tightening all the grounds throughout the car doesn't get rid of it, most auto part stores sell a big capacitor that you can put between the hot and return supply leads of the radio to filter out the noise.

I'd go with tightening and cleaning up the ground leads first, though.

Hope this helps,

Moonraker

I had exactly the same noise when the power lead to the antenna amplifier came adrift. It is a single wire coming down the outside of the antenna co-ax.

Dunasso

I've tried to clean and resecure the grounding wire and also the power lead but the noise still pursists. However, the antenna could be and issue as I had the windscreen replaced about 2-3 months ago. I'll pop out the glovebox after dinner and check the connection there.

Thanks Bob, Bill, and Eric,
Duncan

Bill Wagner

Dunasso:

Ideally, ground signals are all at "earth" meaning that if you took an ohm meter and measured from one grounding point to another they would all read near zero ohms. When a problem exists where one (or more) ground connections doesn't meet this requirement, the offending points can actually induce a signal into the ground. This point doesn't nessecarilly exist at the supply leads of your radio. In other words, ANY bad ground connection can induce the signal, not just those connected to the radio. If this is the case, the fix is to verify that all ground points throughout the car are good (no corrosion, not loose, not oxidized, etc).

The problem could also be electromagnetic interference (EMI) most likely being generated by the ignition system. This would imply bad shielding in some of the components, or even a breakdown in the spark and/or coil wires themselves. One quick and easy check might be to move the wires around and see if it changes the intensity of the noise. Needless to say, move the wires with the car off..maybe tie them or somehow fix them near the engine itself in some way.

Hope this helped,

Dunasso

Bill, I've decided that noise is engine related. When the revs are up, the pitch gets higher and when they are low, the pitch gets lower. I've redone all the grounds and leads, but still have the noise. It was recomended by Bob that I check the antenna leads; they were fine too.

This noise is really carving into my brain. I can no longer enjoy the radio or my CDs. I went to Radio Shack last night and bought a noise supresser, but still no luck, the noise was there this mornig, again.

While driving today I made another observation. The noise seems to get loud then soft and loud and soft at irregular intervals, as if a switch is being flipped off and on. The sound never really goes away, it just overpowers the radio and then softens to the background, but it's still there.

Does anyone know of any electrical devises that come on and off that cause this feild Bill is describing?

Duncan

Bill Wagner

Is your air conditioning on?

JasonAndreas

There is a noise suppressor for the ignition system in the rear fuse box but I don't know if it could go bad.

Eric Kessel

Did you try disconnecting one of the coil control modules at a time to see if there is one bank of plug wires that has a wire going bad? Just a thought...... Also, is this a factory radio/amp?

Dunasso

Bill, the AC compressor and fuse have been removed.

Jason, I was unaware of a supressor. Any one know the exact location? Is there a way to check it?

Eric, I have an after market stereo with 2 aftermarket amps. They have been in the car for about 3yrs. The radio is wired to the factory supply and ground harness, which has been checked and rechecked. The 2 amps are connected directly to the battery for the exception of the switching wire that runs between the radio and amps. I was told that it is best to have the amps directly connected to the battery. The supreesor that I mounted the other day, is connected to the radio leads. I have not installed any for the amps.

Someone at work mentioned that they had a similar problem with their non-Porsche car that turned out to be the alternator. My alternator is original as far as I know. I've owned this car for over 7yrs now, but it could have been replaced by previous owner, however I have no documentation of it. I will assume that it has not.

Does anyone agree with that assesment? Should I disconnect the alt. to check this out?

agentpennypacker

I have a simple in dash aftermarket CD player that has the same problem. No amps.

I'm wondering if it may be the ground from the radio/reciever itself? Perhaps a new radio would fix the problem here?

Dunasso

Eric, I did as you suggested, by disconnecting the coil moduals one at a time. I only succeeded in making the car run worse. Although the noise did decrease, it did not go away.

A.P.P., I thought pretty much the same thing too, however, I didn't really want to experiment with a new $400.00 radio. I have disconnected both amps from the batt completely, and the noise still persists. So, I am begiining to think that you are possibly right, it may be the radio after all. The only things that I haven't tried are, rewiring the radio directly to the batt, and disconnecting the alt.

I'm hoping that someone can help me out with the factory supressor that Jason had mentioned. Is there a way to test it?

Dunasso

Indycam, the noise is constant, it never stops. Whether the volume is up or down, when there is a CD playing or if it is just the radio. As long as the unit is on, it makes the noise. The sound is coming out of all speakers, even the woofers. It is a high pitched squeal that gets higher as the engine revs up. Sometimes the noise gets loud, overpowering the music, but most of the time it is a steady squealing in the background.

I thought like most that it would be a simple fix. But, it has turned into an every afternoon event to locate the source.

I thank everyone so far for the input, but again I am still at a loss.
Tonight I am going to remove the alt belt. If that doesn't work, then throughout the weekend I will rewire the radio straight to the batt. If that doesn't work then I'll set the car on fire!!

Duncan

Jeff PE

One other possibility - as I experienced it - is a bad antenna lead (actually, bad shielding on that lead). Bad news, at least on my 1990 C4, is that the original lead and booster are one piece whereas the replacement requires that you buy both as separate items and the latter was on back order. Jeff PE.