Xbox 360 lights are green but it says mode not supported on the tv screen -no picture at all -even tried another tv and heard the audio at times but no picture-all cords intact-no ventalation problem system a year and half old.

Are your controllers connected to the xbox? that is how you get green light bars around your main green light bar. If you are not refuring to this and nuthing is showing up on your tv screen but you have sound try ajusting/ spinning around the yellow av cord ( Yellow cord is what projects pictures onto screen) . Hope it helped. =]

Red Lights are a problem for Xbox 360, however green light problems are hard to find, still you can try following steps to check where the problem lies

1) Boot with no HDD and see if that helps.
2) Also remove all your inputs in the back, and reinsert them. Make sure your HDMI/VGA/Compenent input is plugged in correctly.
3) Try switching the output from HD to SD, if you have a HD VGA Cable for your Xbox 360
4) Turn the Xbox 360 off, turn it on with the controller, as it turns on hold the Y button and the Right Trigger, this will put all audio/video settings to default.

If the above given steps do not help, kindly call Microsoft Support and try to get an answer from them to this issue, and if required you may have to send your console for repairs.

Follow the steps below, Hope this helps

1. Try another Av cable ( Audio video Cable )

2. Try another television

3. If the steps dont work, call xbox customer support to have your xbox serviced. Good Luck! hope your console still has warranty

The main reason why its acting that way its possible that the AV PORT is faulty or its your cables..

Since you already exhausted all the steps to isolate the problem, The probable causes of this issue is the AV PORT is faulty.

You might wanna contact xbox customer support to check the warranty status of your console, hope you still have warranty so that you can send it in for free.. Goodluck

Follow the steps below, Hope this helps

1. Try another Av cable ( Audio video Cable )

2. Try another television

3. If the steps dont work, call xbox customer support to have your xbox serviced. Good Luck! hope your console still has warranty

This issue means that your xbox 360 console is having a problem with its Video Card.

your courd that goes to the tv is probably shot or you have the switch on the courd on the wrong setting

it sounds as if you have a connection unhooked or loose somewhere. Double check all audio and video cables are secure and in the correct position. If that doesn't work try troubleshooting by trying a different tv or removing all connections from tv and xbox and re-hooking everything back up.

They are green?!? usualy when people have problems with  the xbox 360 hardware, the lights turn red. This xbox 360 may have a birth defect... Best thing to do is call 1800-4my-xbox. Talk to a representative about sending your xbox in, ONLY if you have not voided the warranty. If so, you will most likely have to buy a new xbox or new motherboard for it.
Also try changing your video settings to tv instead of hd, or hd if it is plugged into a hd tv. You might have toggled the HD switch on the video/audio chords.

where you put the cables for the sound and picture if you look on the end where you plug it into the xbox 360 you will see a little switch it has HD and TV on it depending on what your tv supports (HD ready TV) (normal TV) switch that switch to what TV you have (e.g. HD TV, switch the switch to HD) if that doesnt work then try checking that you have all the cables in the right ports if you have pluged the HD cables into a normal TV then this is not going to work, check cables and check the switch!

its overheating but will give u red light eventually try googling X-Clamp fix i fixed many with same problem