CT_A6_guy

its a 2000 A6 4.2 with the Bose system. When listenening to low power stations there is a distinct motorboating sound when the station is weak. If the engine is off, the motorboating sound is gone. It doesn't do it on strong stations and everything else seems ok.

The service guys checked it out and said everything was to factory spec. But it still has the problem.

Any ideas?

Thanks in advance!

Alan

PaulW

...if somebody competent is working on it. I would say bring it to a radio place instead of a dealer.

Courtesty of Hisport:

Radio/stereo noise can drive you bonkers. It used to be - back in the
bad old analog days - more of a problem than it is today. Your digital
Concert radio should be dead quiet.

Thankfully, radio/stereo noise is generally pretty easy to diagnose.

Sources of noise are:

1. Radiated (ie, strong EM signals which overcome reception clarity.
Like a bad engine ignition coil or someone arc welding close to your
vehicle)

2. Conducted (ie, electrical noise in the vehicle 12 VDC system. Like an
open alternator diode, accessory motor capacitor, poor ground or power
connections)

3. Reception (ie, poor antenna system or radio receiver section. This
will allow radio to receive noise vs. clear signals)

First, check your that your battery connections are clean and tight
(trunk, RHS). Then, replace your radio fuse with a new one (fuse panel;
see owners manual). Then, begin eliminating noise sources until you
track down the culprit - see below.

If the noise changes pitch with engine speed, it is either radiated
(secondary) or conducted (primary). If the noise is coincident with
turning on the ignition, but not starting the engine, it is almost
certainly conducted. If the noise even occurs with only the radio on -
everything else turned off - it is a reception problem.

If the noise seems to be coming from the engine, open your hood and wave
the antenna of a portable radio (eg, boom box turned up loud) over the
running engine. Interference noise tells you it is a radiated ignition
secondary problem. Easy to diagnose from here by pulling VAG codes
and/or scoping engine.

If the test radio stays clear, the engine noise is most probably coming
from the alternator. Check alternator connections and capacitor pigtail
under car. If still noisy, pull the serpentine belt to eliminate and
recheck.

Noisy with ignition on; engine off? Turn off the AC/heat, etc until the
noise goes away. Source is probably an accessory motor. If you have
solar panel sunroof, put a towel over it to eliminate cabin recirc
motor.

Still noisy? Replace the radio after verifying all antenna and power
amplifier connections.

CT_A6_guy

Its at the Audi dealership I bought it from. I have to hope they are competent. I WILL check the things listed and see if it helps.

Thanks!

john in cincy

you should be happy you can hear low power am stations at all (vbg).

John in Cincy

fkess

There's a bulletin on A4 and A8 about poor reception on AM. Turns out to be bad soldering at antenna on 2004s. Worth a try with the dealer.

Suds

That usually means the battery is old and dying -- it may have the correct voltage but high AC impedance.

But your case is reversed -- battery operation is fine, engine operation is trouble-free! So I would guess that your alternator/charging system is somehow introducing resistance in the power-supply path when the engine is on.

An alternate theory: it is the battery that is bad -- when the engine is running, electrical accessories are placing enough of a load on it to degrade its output but when the engine is off, the battery specs. are adequate.

In either case, I would swap in a different battery and see if the problem persists. If it does, have the alternator/charging system checked, maybe measure the current draw from the battery and compare with a known good Audi.

Lastly, your radio itself may be the cause...

Fla-4.2

save the above - excellent step-by-step troubleshoot !

CT_A6_guy

It does it on FM.. haven't listened enough to AM to notice it there. Its a 2000 model year