How Water? in Technical Tips and Tricks Posted February 22 · Report reply In my experience, it sounds like your water heater is not sensing the flame after the propane lights. Your description of the symptom fits that exactly. In most cases the fix is to replace the ignitor probe. They usually cost about $20 +/-. A brief explanation of what happens is that the same probe that supplies the spark is then monitored by the circuit board for a very small voltage that will be returned to the circuit board when the flame contacts the probe if all is working properly. The voltage is so small (measured in micro-volts) that most of us do not own a meter that can detect it, but it is there. Several things can prevent that voltage from being detected. It is possible that it is just a poor connection and that if you clean the contact where the probe attaches to the circuit board well, it may work again, at least for a while. Another thing that sometimes causes the voltage to not be detected is for the ceramic insulator of the probe to have a tiny crack that is filled with carbon and shorts out that voltage, or it may have failed and no longer supply that return voltage. Whatever you do, do no use a small wie o clean the gas jet because it will probably be damaged by doing so. If that jet looks dirty clean it with alcohol and do not use anything that is abrasive on it.