Disclosed are a hydrogen generator and a method of producing hydrogen gas therefrom. A fuel unit containing a fuel that releases hydrogen gas when heated is removably disposed in a cavity within a housing having a door. A heater assembly for heating the fuel unit is disposed in the hydrogen generator. A mechanism retracts the heater assembly from the fuel unit when the door is opened and extends the heater assembly to contact the fuel unit when the door is closed. When the heater assembly is retracted, more space is available into which the fuel unit can be inserted to prevent damage to the heater assembly and the fuel unit, and when the heater assembly is extended, good contact is provided between the heater assembly and the fuel unit for efficient heating. A cam bar can move the heater assembly normal to the lateral motion of the cam bar.