Originally Posted by "007"
Most likely its carbon build up on the ceramic heat sensor. Carefully clean off carbon with paper towel or a contact cleaner. Try not to brake the sensor and clean after the heater cools down.
Right on the money 007, you took the words right out of my thoughts. One important thing to remember, if the IGNITER has carbon build up on it, once you remove and clean it, you should adjust the FLAME after you light it. Real simple, the round pipe that feeds the fuel, has a slip joint right in front of you next to the access door. Once lighted, loosen the small screw that you will see close to the slip joint with a pair of pliers, just enough so you can slide the slip joint with your pliers. You will hear the flame sound change as you move the slide just a small amount. I like to get a pretty good ROAR from the flame, it keeps the carbon build up down, tighten screw, WOLA, your good to go, JMHO, it works for me. Good Luck.