Quote Originally Posted by danpik View Post
I am still thinking it is related to the flame sensor. When the electronics in these heaters allow the gas valve to open they essentially allow the heater to run in a mode that bypasses some of the safety features (flame sensor) for a set amount of time. Usually about 10 seconds. This is to allow for the flame to establish itself and be present for the sensor to "see" it. If the flame sensor proves good then the control board will allow the valve to stay open. If not, it will shut down and try again for a pre determined amount of tries. Usually 3. If you were able to get to the sensor to clean it you should be able to see the burner associated with it. Since flame sensors rarely ever go bad (other than needing to be cleaned) I am going to guess the burners need to be cleaned. There could be a spider nest in the tube that feeds the burner head or rust/other debris blocking the gas flow in that area.
Did you ever get this issue resolved? I have (what appears to be ) the same issue - I replaced the igniter, but still no luck. I don't see flame through the peep hole.