Are they fluorescent lights? I've had to replace about 6 tubes in my 2004 Monaco.
Have you tried swapping out light bulbs/tubes with known good ones?
2004 Monaco La Palma 36DBD, W22, 8.1, 7.1 MPG
2000 LEXUS RX300 FWD 22MPG 4020 LBS
Living is hazardous to your health.