Is it a random noise or is it kind of "periodic" and happens at a set interval? (like a tick... tick... tick...)

If periodic, there are some small "ice cube" relays in the fuse box. If they click, you can hear them from the drivers seat. Open the fuse panel after this has been happening and see if one of the small silver relays is really hot. My power seat made this happen at one point.

Have you tried disconnecting the speaker or fading it to the rear when this happens? Bad speaker or speaker wire could certainly cause this.

I've also had two W126's where the hood hinge bolts loosen and hinge vibrates. Only seems to happen on the drivers side. If you see the left rear edge of the hood vibrating when at idle (the area at the bottom corner of the drivers side of the windshield), try tightening these two bolts.

Neal

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