Strange noise from LF speaker(TSB on fuel pump noise)

[jlsumme]

Just completed a two amp install on my 99 taurus.Everything was fine with the first amp pushing the subs but with the second amp for the other 4 speakers I have noticed a RANDOM loud squealing noise coming from the left front speaker.This noise usually starts upon start up and the only way to stop it is to turn the car off and re-start and the noise stops.The noise is also present with the CAR TURNED OFF with the key in the acc position.On one occasion the noise started after start-up and had to pull over.The noise is loud and turning the radio off does no good.The second amp is the cause but I can't understand why.The noise is gone when the amp is disconnected.The system sounds great most of the time.I saw a tsb on fuel pump noise for this model taurus.Could the location of the amp be to close to the fuel tank?

[sfontain]

Well I'm not an expert on electrical noise but unless you have a very sensitive amp or ran your wiring strangely it seems unlikely, particularly if turning off the engine and restarting fixes it; the pump will be getting power and running just like it was before you turned off the engine.

Firstly, see if it happens when you just turn the key to ON without starting the engine so that your system turns on. The fuel pump will turn on for only a couple seconds until the system pressurizes; if the squeal occurs and doesn't change as the fuel pump spins down, it just doesn't seem likely to me. And if it were the pump I would be more inclined to expect static and/or a humming noise from the speakers.

Also, your fuel pump is, I believe, directly under the rear seat cushion, so if you put your amps somewhere anywhere in the trunk (as the vast majority of people do), they aren't really that close to the pump.

Others may have ideas to fix this. Good luck.

[TomV]

You mention the noise coming from one speaker of the four connected to the amp. I would then assume the other 3 speakers do not exhibit the noise. What is the amp configuration? Are there two channels with two different speakers connected to each? If you had a bad channel I would expect two speakers would sound bad.

How are the speakers wired to the amp? Are there separate pos/neg wires between each speaker and the amp or is the neg (ground) of the speaker and amp connected to a nearby chassis point? Separate ground wires eliminate the typical ground loop problems that come with tying the signal return lines to a convenient chassis point.

The fact that this is seemingly random in nature and can be reset by shutting things off leads me to suspect the amp itself. Try eliminating the car components by shutting off only the amp in question (removing the fuse or the blue control wire) and reconnecting it back. If the problem goes away as when the car is turned off and back on then this leads directly to the amp. If the problem does not go away then there may be a car component that cleans itself up when it is turned off. Some of these problems can be heat related. Turning the amps off can clear them up temporarily. As they heat up then they become noisy again.

The amp for the subs could be the culprit. The low-pass filtering of the channels would suppress the noise to an inaudible level through the woofers, but connecting normal wide range speakers would show the presence of the noise. My son had a similar problem with his sub amp while waiting for a replacement sub. The wide-range speakers showed the noise, though to a lower level, even though the amp's low-pass filter was used. The noise was not heard once the new subs were connected since they could not reproduce freqs much abouve 1000 Hertz.
The sub amp could be generating this noise on its power line or ground line and being picked up be the other amp. In other words, each of your amps should be tested individually.

[jlsumme]

Thanks for the info, well i need a new amp.since I posted the amp in question will now turn off when turned up thus no more noise.This amp is an old sony 205 and it was connected to the front speakers.