no display

For about a week the PC monitor was working off and on. Now when I turn on the computer and monitor, the light on the monitor will go green for 1 second and then go yellow and I have a dead screen. I cant even see the bios screen. The pc is running and “sounds” normal. Its has an agp video card. Monitor is about 2yrs old. I re-seated the card and connections. ???card bad???