I have an Audiovox MMD11 overhead monitor with DVD player on my car. I can not play any DVD it comes out with bad disk every time I try

SOURCE: Bad Disc Error

TAKE A LOOK ON YOUR LENS MAYBE IT WAS NEED A CLEANING CLEAN IT W/A COTTON BUDS CAREFULLY OR OBSERVE CENTER MOTOR IF ONCE YOU ON YOUR VE700 IF IT SPIN ALITTLE BIT IT REQUIRED YOU TO CONCENTRATE ON LENS AND MAYBE YOU TO REPLACE IT

SOURCE: audiovox adv 300 dvd player with stuck disk

let the technicians get it our for you, to prevent damage on your player.

SOURCE: audiovox DVD overhead Monitor

the power supply amperes might be too low try using car batt as your power source

SOURCE: Audiovox D1020 DVD player won't read DVD anymore

I have the same problem! The only way to fix this is to replace the motor that spins the DVD. if you take it apart and spin the DVD the movie will play. The motor is just wore out and has no torque to start the play process. I am still looking for a replacement motor for it and haven't found anyone that carries the motor required. Only Audiovox so far and they want 180 to send in and fix.

SOURCE: overhead DVD monitor screen dead but sound plays through stereo

If it's a Rosen dvd player the dvd will need to be put in the unit itself & not the unit in the dashboard! The dvd player mounted in the head ligning is a seperate unit from the stereo system fitted in your dashboard!
Sounds to me like you are putting a dvd into the dashboard stereo system which will play any audio through the car speakers...
Put a dvd into the Rosen unit itself & i am sure you will get a picture on the drop down screen! Remember that as far as i know all Rosen dvd players transmit the sound from the dvd to infra red headphones that should be included! Remember to check the batteries if you still can't hear any sound as they run down quick if the headphones are left on!

Hope this helps....