I really need to get my car in to have the radio checked, but I figured I would post the question here to see if anyone else has experienced this problem.

I have a stock 1 U stereo in my car (the one without the IPOD connection, but does have an auxilary jack. I have the volume controls on the steering wheel as well.

The problem I am experiencing is that occassionally the volume will decrease while the car is running. Its pretty subtle, bt I sometimes catch the radio display showing a lower volume number until eventually there is no sound. Has anyone else had this issue?

I am positive I don't have any volume control (increase while driving) functionality with this deck.

if you can get it to duplicate for a dealer, i would say take it in. something seems to be wrong the wiring in the head unit. i see it is an 09 so im assuming you arent over 36000 miles yet(hyundai only covers the radio for 36000 miles).

yup thats all they cover it for and you have to get to happen for them, cause they will just tell there aint a thing wrong if they check by themselves, as for the radio my 07 does the same thing, so i put a pioneer in, no steering wheel controls to begin with otherwise would have left deck in and paid the 100 to have if fixed, ive read the manual over like 3 times and none of the radios come with sav,speed adjusting volume.

I've been having an issue with the radio in my '10 SE as well. The first radio I had would drop XM after about 5 minutes so I had it replaced under warranty. Now I find after about an hour of the radio being on, car running or not, there is a high pitched squeal that gradually gets louder longer the radio is on. It eventually is unbearable and is heard even over loud music. As soon as I hit the power button on the radio it goes silent. I had the radio replaced and the issue remains. The original radio definitely did not have the problem-needless to say I have yet another appt at the dealer.

problem is... i can't reproduce the issue to easily... And... if you take it there and they send you away, I find you end up wasting so much time unless the problem occurs 100% of the time...

I can replicate it 100% of the time. I always thought that it was an undocumented feature of the Elantra. The volume always decreases when I'm at idle, gets louder at 40 mph and it's where it should be as far as volume goes when I'm above 55 mph.

So I am now on Radio number three almost two years later with the SAME ISSUE.

I did seek out this problem, and apparently the default radio volume can be adjusted.... I have not tried this yet, but will tonight:

-turn the radio on
-adjust the volume to display the volume level on the display
-push and hold the powerknob until it beeps or the display flashes
-turn the volume knob to the desired level
-push the volume button again to set the level

Interesting, I eventually thought that it was the lack of power being supplied by the alt since it always seemed to get lower at idle and increase when I was accelerating. I'll have to check that out.

Huh. Good to know. I wonder if that would work on my aftermarket H/U?

I'd also like to throw in my remorse. Audio issues suck, especially if they are repetitive even after trying to fix them multiple times. I hope everything works out