RV Repair: RV water heater, propane water heater, burner flame

Question
My propane water heater starts and runs for about 3 seconds then shuts down. It will do this twice after turning the main switch on. It does not run beyond the three second limit. Whats wrong , any clues.

Answer
Hi Bob:

When the main burner of your water heater comes on, there is a sensor probe that the flame hits, then a signal is sent to the control board telling it that the main burner is lit. If the flame is not hitting the sensor probe properly, or if the control board is defective, you could experience this type of cycling action you have described. The reason it tries twice, then shuts down totally, is because of the safety factor built into the controls,that limits the restarts. Please look at the flame sensor making sure it is in the edge of the main burner flame. If you still need further help, please let me know. I will do my best to assist you.

Regards, Larry