took this from rv fridge site :
Works on 110 VDC but not on propane, then try this:
•The first step is to determine if you have a good quality flame. If the flame lights but goes out almost immediately, the thermocouple which acknowledges the presence of a flame may have failed. This device is attached to the main gas valve at the back of the refrigerator and has a tube extending to the vicinity of the gas burner. In most instances, this can be replaced by an owner with some mechanical ability.
•If the flame stays lit, the next issue is the quality of the flame. Often rust and debris will fall from the vent interfering with the burner system. I personally have experienced this problem twice, causing the burner not to light at all. To fix the problem only requires removing a minimal amount of tin shielding and then vacuuming the area around the burner thoroughly.
•If the flame fails to light, vacuuming the burner area may clear the port (or jet) of the burner. Worst case scenario, run a very thin wire into the burner orifice to clear debris. Because a small steady flame may not be the proper flame, I recommend cleaning the area with a vacuum in every case of failure.