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Weird radio noise about 30 seconds after I start the car


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This is an annoying thing - that is so trivial it is almost not worth asking about - but annoys me enough that I wonder if its only happening to me or to everyone.

2009 C4S. 31k miles. I've owned for a year or so.

Every time I start the car and pull away, after about 30 seconds of driving the radio makes an odd squelching noise for about 3 seconds, and then returns to normal. It is most noticeable on FM stations. I've owned a lot of cars and I've never heard anything like this.

Does this happen to anyone else. Any ideas what causes it?

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I have a 996 but if 997 is the same, then it could be the SAI pump, which runs about 30s when engine is cold. Does it happen when the engine is warm? Maybe when the SAI pump is powering down it creates some static? It's a WAG.

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James. This is most definately not normal. Modern radio/nav systems are well isolated from noise entering through the power line. It is as simple as putting a capacitor of the right size (depends on the systems impedence) across the power line. If this is bad, and caps do fail, you probably will hear all kinds of stuff such as the pump Ahsai mentions. Things are constantly turning on and off and some items are noisier than others. But, a well isolated radio should "hear" none of this. A dealers response to this would probably be trying to replace the PCM at a rediculous cost. But, I bet any good Nav/radio installer could easily put an additional filter on the power line at relatively minimal cost. They see this problem all the time. Good luck and let us know what happens!!

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I was thinking more about the radio picking up the RF noise generated by the simple DC brush motor. One simple test is disconnect the SAI pump and see if that makes a diff. You may trip a CEL but that should reset automatically once pump is plugged back in and the car driven a few cycles.

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