So i have a rx-v3900 everything works on the unit and the remote works with everything else except the 3900.
Do you mean the remote for the 3900 works for other devices, like a dvd player, but doesn't work to control the receiver itself?
It's possible the IR sensor on the receiver is bad, but not likely.
- Use fresh batteries in the remote.
- Make sure there is nothing blocking the sensor on the receiver. If the receiver is in a cabinet with smoked or very thick glass the IR emitter on most factory remotes is often not strong enough for reliable operation through the glass.
- Most factory remotes also have a very narrow angle over which they transmit the IR signal, typically +/- 20 degrees, so when off-axis it may not work as well.
The remote for my Onkyo DVD player didn't work worth a crap unless I was right up in front of the player. My URC MX-350 universal remote will work from practically any angle even from well over 30 feet away in the kitchen. So you might consider purchasing a good universal remote.