Fantine

I have a 2007 Elantra SE. The radio has recently developed a weird
problem. I almost always listen to my iPod via a cable in the aux
port. The volume is supposed to slightly lower when the car slows
down and stops, and then increase when you accelerate. Now, the
opposite is happening: the volume increases when the car stops and
decreases when I accelerate. I'm going to ask about this when I bring
the car in some preventive maintenance in a few weeks, but I was
wondering whether anybody else has had this problem (and also whether
it's covered under the warranty). Thanks.