Please give us a call at 1-888-388-6372, and a member of our sales team will be able to source the correct parts that will fit your particular set up.
Either the thermostat or high limit sensor is defective and will need to be replaced. Attached is a video that may help identifying the problem. http://www.youtube.com/watch?v=BhGyDXzk6IM
We should be able to get you one that runs on propane, we just might have to special order it. For details, please call our sales department at 800 447 4941 x2.