Audio Systems: Volume goes up/down on its own., Yukon Denali hi low interface

Question
Hi,
  I have a 2005 Yukon Denali with stock deck.  I got 2 12" JL Audio subs installed a few months back and everything worked fine.  Few weeks ago I noticed that the volume while listening to cd's or the radio changes drastically (the door speakers and subs also) on its own.  I got it looked at and got the high/low converter swapped out thinking that I might of got a faulty converter.  It was ok for a few days then the same problem started happening again.  I've had the wiring checked for shortages and subs and amp checked also and everything is fine.  I was told it has some thing to do with the deck.  I have now unhooked the subs because I have a warranty on the vehicle that would cover the replacement for a new cd player.  Without the subs you still hear the volume change but not as much, since the subs are not hooked up.  The dealership did some test and could not find a problem with the deck.  Is there anything I can do or you suggest to try and fix this problem?  Thanks!!  

Answer
The problem is your hi and low interface, most shops don't know what to use in a vehicle
there is only one for your radio ,

http://www.oemautosound.com/c-135-gm-chime-retention.aspx


also there is a sensor in the radio that turns up the volume if the windows are down or if there is to much noise
lets hope the other hi/low didn't damage the radio