Audio Systems: 2001 Ford Focus Radio, spark plug wires, duty alternator

Question
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Followup To
Question -
How can I eliminate the loud static when listening to an AM station in my 2001 Ford Focus?  The FM stations are fine.
Answer -
John,
The static that you hear on the AM stations is coming from electrical noise from your vehicle and from outside sources. Some better made stereos can filter out most of the noise and make listening to most AM stations possible. To test for electrical noise coming from your car's electrical system try this test. Put the ignition key in the accessory position and then tune in AM radio stations. With the key in the ACC position the car's engine computer will be off, the computer generates the most electrical noise that the AM tuner will pick up.


TOM,
T&D ELECTRONICS
tdeser@zoominternet.net

Thanks Tom.  The most noise comes with the engine running.  The computer does not seem to have any effect at all.  Can you recommend a filter that can be put into the power line?  Where can I purchase it?

Thanks again

Answer
John,
Two sources of noise are 1-popping/clicking at a rate depending on how fast the engine is going. 2-whining from the alternator that goes up and down with the speed of the engine.If you have mostly the popping from the spark plug wires you will need to have installed special wires and other ignition parts that will help quite down the noise somewhat. Noise caused by the alternetor that produces the telltale whine can be completely filtered out with a heavy duty alternator filter. You may be able to find these heavy duty filters at most larger auto parts outlets. You may also find heavy duty/high current filters at a marine store. The filter that you install or have installed must be rated at least to the output current of the alternator on your engine. Filters for alternators are to be installed on the alternator, between the alternator and the large output wire that goes to the battery. Putting a filter in the power lines to your radio or other electronic items will not remove the noise.

TOM,
T&D ELECTRONICS
tdeser@zoominternet.net