Bose system high frequency noise 1996 Seville

[stefank]

Hi Folks,

some of you might remember that I was (yes WAS) plagued with a high frequency noise in my 1996 Seville. I tried several ways to get rid of that noise (shielding wires, re-routing antenna cable etc.) but to no avail.

Now I finally found a workaround and got rid of the noise.

If interested, read how.

Car in question:

1996 Cadillac Seville SLS with RSS suspension and Bose-Audio-System

Problem:

High pitch sound from radio speakers even if the radio is off. This noise is not present when the car is at rest with the engine running, it starts right when the car begins to move and is present all the time during driving, sometimes the frequency changes due to various suspension settings.

Since I have very good ears (don’t listen to my wife regarding this point), this noise drove me mad driving around town. Freeway driving no problem, as there’s more road noise present.

If the radio is switched on, this noise is still be present, but no longer audible because of the radio output.

Reason:

The RSS suspension is sending signals from the PCM behind the rear seat to the shocks at all four corners. This signal is fetched by the constantly powered Bose-Audio amps which are located at each speaker, you’ve got four of them.

Diagnosis:

1)

Pull “AMP” fuse in trunk compartment fuse block, this will deactivate the Bose-Amps.

Drive and listen. The high pitch noise should be gone. No radio sound. No audible warnings (lights on etc.). Replace fuse. Drive and listen. High pitch noise present. Radio and audible warnings work. This will set no codes.

2)

Pull RSS fuse in trunk compartment block, this will deactivate the RSS suspension.

Drive and listen. The high pitch noise should be gone. You will get the “service ride control” message and a code may be set. Radio and audible warnings still work.

Replace fuse. Drive and listen. High pitch noise present. Clear codes if necessary.

Remedy:

Alternative #0

Rip out whole audio system and install GPS-DVD-Entertainment system from reputable company. Con: $$$, sacrifice well working audio system, much work.

Alternative #1

Install a noise supression filter in the power feed of the Bose amps. I did try that, no success. Forget it.

Alternative #2 / my solution

Deactivate 3 Bose-Amps (RF, RR, LR) while radio is off, leave front left Bose-Amp on. This will reduce the high pitch noise by most, and the audible warnings will be active.

This is easiest be done by switching grounds on and off by means of a relay energized by the radio antenna power lead to detect radio operation.

Diagram #1:

http://exoticars.de/seville/bose/bose1.jpg

There is a ground lead for every speaker amp under the rear bench. They have to be identified,cut and wired with the relay.

To do so, remove rear seat cushion and seat back. If you lift the sound padding under the rear bench on the right (passenger) side you will see a black, flat plastic channel, running front to back, which hides a wiring loom. It is secured with plastic tape, remove the plastic tape and lift off the channel top. You are looking for four thinner black cables (going to the four amps) and one thicker (ground supply) which are crimped together.

Two of the thinner black cables leave towards the trunk (left and right rear amps), one follows the plastic channel you have opened to the right front amp and the last thin one vanishes into another plastic channel (together with the thick one) across the car to the left side, this is the front left amp ground line.

We want to switch off the following amps: Right front, right rear and left rear.

We want to leave alone: Left front, as this will supply us with the audible warnings.

Cut the following wires:

- two thin black wires running into the trunk where they are crimped to the thick wire

- one thin black wire which follows the channel we’ve opened to the front of the car.

Rewire thes cables per the following diagram, check that they are still long enough that they will fit into their locations in the channels.

Diagram #2

http://exoticars.de/seville/bose/bose2.jpg

Now we need a positive feed for the relay, it should be hot with the radio on to ground the speaker amps. The power antenna lead comes in handy.

It is a thin, dark green lead which comes from the trunk and is routed through the opened plastic channel. In fact there are two dark green cables, you have to find the right one by switching the radio on and off. Splice a new cable into this line and connect it to the relay as shown above.

Now we are done. Tape all connections (or use shrink tube) and tuck the relay out of the way, I taped it onto a wiring loom. Check sound at each amp with radio on. Check for audible warnings (i.e. lights on) with radio on and off.

Drive test whether high pitch noise is gone. It should be! Heureka!

Reinstall plastic channel and tape it shut.

Reinstall rear seat bench.

Since we are playing with grounds her, I thought it’s not necessary to disconnect the battery. However, remember whenever you work with the electric system, you should remove the negative connector from the battery.

I wrote this down from my own experience, and I tried hard not to make any errors.

If you do this modification, I can not be held responsible for any damage which may occur during or after the process.

I can assure you that it worked well on my ’96 Seville SLS German spec.

Tools needed:

Soldering iron

Electric pliers

Crimping tool

Material needed:

Relay 30amps

Connectors as needed

Wire

Time to perform modification:

2 hours

[Marika]

Nicely done!! Bravo!!

[jhall]

Stefank,

I remember this from months ago.

Nice job on tackling the problem!

[stefank]

Thanks for the kind words.

It was annoying me to a point that I was considering selling the car. It felt like you were suffering from tinitus.

Now I like my car much better!

Stefan

[MAC]

I have the same problem with my '05 STS. A couple of weeks ago a high pitch shrill suddenly appeared. I thought it might be the backup sensor, but when I isolated the noise I discovered it's coming from the subwoofer. Even with the radio off this obnoxious high pitched shrill (which is not always the same pitch or loudness) randomly appears. I played around with the radio to see if I could isolate what might be causing it, including lowering subwoofer level, switching from rear to front speakers, etc., but nothing helps. At this point, I want to find out exactly what the problem is. Maybe the subwoofer needs to be replaced or maybe a transistor or something inside the amp or radio is shot? I hope I don't have to replace the radio. If only the subwoofer needs to be replaced then I will consider myself lucky.

[BodybyFisher]

In the older BOSE systems the capacitors swelled up and caused that high pitched whine, dont know if that is still the cause, but I had saved this thread, see if this helps anyone who has a whine in their BOSE system

http://www.tahoeyukonforum.com/forum/showthread.php?t=33445

[MAC]

In the older BOSE systems the capacitors swelled up and caused that high pitched whine, dont know if that is still the cause, but I had saved this thread, see if this helps anyone who has a whine in their BOSE system

http://www.tahoeyukonforum.com/forum/showthread.php?t=33445

Thanks for the thread. I noticed one poster said his problem was associated with bad wires in the steering column. It just so happens that I need to replace the turn signal assembly since signaling to make a right turn will cause high beams to go on. The left turn signal is fine. Yesterday the high pitched whine appeared on the way home from work. I stopped to fill up with gas, so the engine was off for about 5 minutes and was gone when I restarted. On other occassions I would turn off engine then restart about 30 seconds later but the whine was still there. So, it seems that the whine will go away if I turn engine off a few minutes or more. Maybe this is evidence that something had sufficient time to cool down, such as capacitors? I'll try to determine if longer shutdowns have a definite effect as far as causing the whine to stop.

[JimD]

....So, it seems that the whine will go away if I turn engine off a few minutes or more. Maybe this is evidence that something had sufficient time to cool down, such as capacitors?

It's possible that 'something' had an opportunity to cool down, but it sure was not a modern surface mount technology (SMT) capacitor. There is zero current flow through a properly functioning capacitor therefore there is no way for the temperature of that capacitor to rise above "ambient" temperature.

If/when there is current flow through a capacitor, that capacitor has failed and there were be additional obvious symptoms.

Describe the nature of the whine;

constant frequency?

or frequency varies with engine speed?

present in all speakers?

[Cadillac Jim]

If the whine is noise from the car's data bus, and is due to dried-up capacitors in the speaker electronics, the capacitors probably gone open. Most old electrolytic capcitors dry up and just stop capacitor-ing, the don't short out. One simple and inexpensive solution is to replace them with newer designs with parts from from Radio Shack.

[JimD]

If the whine is noise from the car's data bus, and is due to dried-up capacitors in the speaker electronics, the capacitors probably gone open. Most old electrolytic capcitors dry up and just stop capacitor-ing, the don't short out. One simple and inexpensive solution is to replace them with newer designs with parts from from Radio Shack.

Electrolytic capacitors in a modern automobile audio system (2005 vehicle, Post #7)? Not likely.

Electronics has been my game for more than 50 years and the last time I encountered an electrolytic capacitor is in the power supply section of my (ancient but still operational) Heathkit SB-220 RF power amplifier.

[MAC]

Well, today after coming out of McDonald's as soon as I opened the door to get in I heard a chirp and sure enough as soon as I started the car the shrill sound came back. I need to check for codes, which I will do over the weekend.

[Texas Jim]

If the whine is noise from the car's data bus, and is due to dried-up capacitors in the speaker electronics, the capacitors probably gone open. Most old electrolytic capcitors dry up and just stop capacitor-ing, the don't short out. One simple and inexpensive solution is to replace them with newer designs with parts from from Radio Shack.

Electrolytic capacitors in a modern automobile audio system (2005 vehicle, Post #7)? Not likely.

Electronics has been my game for more than 50 years and the last time I encountered an electrolytic capacitor is in the power supply section of my (ancient but still operational) Heathkit SB-220 RF power amplifier.

DELL used them on motherboards till just recently...

It was a common failure on GX270 and GX280 models.

[Cadillac Jim]

Everybody still uses electrolytic capacitors. I think JimD is talking about those big yellow Sprague electrolytic capacitors that were used in electronics until the 1970s or so. Those had big aluminum cans under the yellow cardboard cover, were fragile, and, if broken or leaking, had a formaldehyde smell. The technology has rolled over several times since then, beginning with "dry electrolytic" capacitors in the 1980s. You can't get those old style electrolytic capacitors anymore, and good riddance. They were a necessary evil as long as they were the best alternative, like selenium rectifiers, but that was a long time ago.

Here's a listing of a bunch of different types of the more modern kind, for use in repair and DIY projects:

http://www.radioshack.com/family/index.jsp?categoryId=12648753

For an endless selection, do a web search on "electrolytic capacitors." But you won't find any wet electrolyte capacitors like I believe that JimD is referring to.

[JimD]

I'm still waiting to hear from the original poster re my questions in post #8.

Meanwhile, not to beat this electrolytic capacitor issue to death. But, the primary (only?) reason to utilize an electrolytic capacitor is the physical size vs capacitance unit cost issue. At some price level, the smaller package is coveted.

No one who has replaced an ancient oil-filled power supply section capacitor and repaired the collateral damage mourns the demise of 'wet' electrolytic capacitors.

JimD was using the example of a piece of an 'older' piece of electronic equipment that required transforming and rectifying an AC voltage to the DC voltage needed to operate vacuum tubes.

None of which is required by modern solid state electronic equipment designed to operate from batteries or other flat-line DC sources.

[Cadillac Jim]

I did TV repair in the 1950's and have done my share of clean-up from exploded capacitors, smoking selenium rectifiers and the resulting burnt power supply components, and such things that became a thing of the past once fusable resistors became the norm in power supplies.

The last exploded electrolytic was from a Heathkit adjustable power supply that I built in 1969. I let it sit after a move and put power to it again in 1974 and cranked up the voltage to 50 Volts, its maximum, and the huge output capacitor went out with a bang. It was a second-generation electrolytic but it was hundreds of microfarads rated at something like 100 Volts, and those still lost their ability to hold against leakage if they were left with no voltage for too long. It wasn't a wet electrolytic so it didn't make a big mess, though. The one I replaced it with was no better so whenever I use that power supply, I turn it on with the voltage all the way down and turn it up a few Votls at a time, and watch the output ammeter decline to zero before I turn it up the next couple of volts. Then I let it sit at 50 Volts for awhile before I use it.

I've never had trouble with an oil, paper, mica, Mylar or tantalum electrolytic capacitor that wasn't physically damaged. I had some experience with 1% polystyrene capacitors and found that you could easily damage them because their leads would rotate in the case with little torque.

[MAC]

It's possible that 'something' had an opportunity to cool down, but it sure was not a modern surface mount technology (SMT) capacitor. There is zero current flow through a properly functioning capacitor therefore there is no way for the temperature of that capacitor to rise above "ambient" temperature.

If/when there is current flow through a capacitor, that capacitor has failed and there were be additional obvious symptoms.

Describe the nature of the whine;

constant frequency?

or frequency varies with engine speed?

present in all speakers?

As far as something cooling, I'm not sure. Today, as I opened the door, I heard the sound for a brief moment. When I started, the sound was present. Then I toggled the turn signal several times and the sound stopped. I did this because I read a post where someone said a defective turn signal switch could cause this problem. It just so happens that my turn signal switch has to be replaced. If it happens again, I will try the toggle proceedure again. I'm thinking I have done this before and it didn't work, so maybe it was just a coincidence that the sound stopped. Regardless, I need to replace the turn signal switch. For a couple of days prior to this last incident it's been silent, and it's been quite cool here on the east coast--certainly not a warm spring so far, which I don't mind. It's nice to have some cool spring days.