Audio Systems: squeal from car radio, dodge colt, noise filters

Question
I have a 1988 Dodge Colt E which has factory-installed stereo AM/FM radio.  Recently, there is a loud shrill squeal coming from the speakers when the radio is turned on and the motor is running. There is a change in tone of the squeal when the car accellerates or decellerates. There is no squeal when the radio is off and the motor on; or when the motor is off and the radio is on (using the accessories switch). The squeal can be heard on each of the four speakers. There's never been any repair done to the radio or the speakers.  Thanks for your help.

Answer
Hello Shirley,
Several things may be causing the squeal noise. If this car has a factory installed amplifier for the stereo it may be picking up the noise. Either the engine computer or the alternator is the cause of the problem. Based on the description of the noise changing tones when speeding up or slowing down suggest that the alternator is at fault. On most alternators there are factory installed noise filters inside the case of the alternator. These filters do go bad due to the heat under the hood and from the alternator itself. You have two choices here to stop the noise, one-install a high current filter on the output of the alternator or have the alternator replaced.

TOM,
T&D ELECTRONICS
tdeser@zoominternet.net