Composite video IS the yellow plug and wire. The problem is either in this wire and plugs when you hook it DIRECTLY
to the back of the TV yellow input jack OR
with the yellow input jack wiring on the TV itself. Likely is simply a loose connection.
SOME TV's offer more than one yellow jack input (Video 1 or Video 2) and if you have that option...you could move to the second set of jacks. The red and the white jacks are for the STEREO sound and would need to move as well if you so this to the second set of red/white input jacks.
Joel... I think you are thinking of home video COMPONENT jacks which are 3 wires for high definition video in Red/Green/Blue
Of course the standard coax connection for antenna, cable and vcrs is also present but not too many DVD players allow this connection with is a 300 line low resolution connection. HDMI cables would be the choice of most these days but the RV and auto sound industry does not seem to have caught up to that yet...even though the TV's can accept them.