Check the fuse box. There could be the possibility of a blown fuse that has shorted out, causing the lights not to work. You can look at the Coleman camper manual for the box to see which fuses run what lights or circuits. Follow the circuit to the light fuses and replace as needed.
Check the bulbs. The problem could be as simple as a blown bulb. Remove the light covers and check the bulbs on each connector. Usually a blown bulb is indicated by a blackened center near the bottom of the filament. If the circuit is working on the camper, you will be able to tell which bulbs may need to be replaced.
Inspect the light switches. The problem could be a faulty wire or a short circuit in the positive connections. I would suggest you hire an electrician unless you are properly trained to check wiring. Check for small burned spots on the wiring, which would indicate a short or a possible malfunction.
Inspect the wire connectors from the camper to the towing vehicle. The problem could be within the connecting pieces or a short. It could also be as simple as a loose connection where the two pieces are not fully making the connection.
