no sound out of dvd

[hoffman]

i just bought an 03 excursion w/ factory dvd player which plays but has no sound out of speakers when i push the buttons the radio goes to dual play then i get no sound i cant figure it out any help?
edit:
it also only has sound out of the rear speakers if its in single play, i hear a relay click under the center counsle. the head phones work only on the radio just the same as the speakers.