Triker is dead on, only you may be unfortunate enough to have had moisture get in the housing and rust the bulb base to the socket. If so, make sure your wiring is unconnected and soak the fitting with WD-40 (or something similar) till you can pull the bulb base out with needle nose pliers. Then wipe everything dry and clean the socket and apply some di-electric grease before inserting new bulb. Make sure the light housing base is adequately sealed to the rv and that the lense fits securely.
Daniel & Donna Leonard
2011 Ram 4500 SLT 4x4