Assume you still have the old DHS 12v surround sound system--volume is controlled thru the source, eg, TV of dash radio [think all the connections are RCA jacks]. The switch on your front dash pointing toward the passenger seat may be the problem. This button switches the surround sound from off, to radio [audio], to video [tv]. Over the years, our switch has gotten more and more flaky. Dont know if DHS still makes/has parts for this system or not. A lot of folks have given up on the old 12v DHS system and have gone with a cheap to modest priced 120v home theater system--sometimes you can use the the existing speakers--if you dont crank it up too much!!!!
PS-- advantage of new 120v system is remote card ops, usb iPod connects, and disc player.
PSS--ref the PS, all of these "advantages" can also be gained with a new in-dash radio [if you get the DHS system working].
2003 40' MDTS
Garden Ridge, Texas