1989 Chevrolet K1500 Silverado dome lights and radio stopped working all together?

[Adam Gebke]

I have a 1989 ext. cab 4x4 silverado 1500 and I parked it one late summer night and the next morning I went out to drive it and the dome lights didn't come on when i opened the door. They won't even come on when i use the dial by the headlight switch. Along with that electrical problem my radio doesn't want to come on either. I've borrowed somebody else's working radio and even it doesn't want to work. One last thing i've noticed is that over night something is drawing power out of the battery and if my truck sits longer than 5 - 6 hours its out of juice. My dad and I have guessed a short maybe but not sure. Do the radio and interior lights run on the same circuit?