I also have a #3051S and the using the dash DVD to play the interior TV's is done using component and coaxial cables. First make sure the coaxial cable connections on your TV's are tight.
But my recommendation is purchasing a blu-ray player and connecting it directly to the TV using a HDMI cable. This will provide you the BEST
quality DVD picture using standard DVD's or blu-rays DVD's.
Remember a blu-ray player
upscales a standard DVD movie. You may notice the picture on the in dash monitor is excellent when playing a DVD in that unit. But the signal quality is reduced when it is played on the HDTV's.
Do yourself a favor and purchase a blu-player and HDMI cable for you main Living area TV.