Worked on a set of gas logs yesterday for a gentleman. Don't know a whole lot, though I have worked on logs from time to time, but usually it is the thermocouple needing attention or a problem with the thermopile or too much resistance in the control wiring, etc.
Initial problem according to the customer is that the logs would cut off after about 15 minutes of run time. When they turn off, it cuts the pilot and main off. I found the thermocouple to be very dirty, so i cleaned it with sandpaper and cleaned the thermopile off as well. So I was thinking that if the this is like regular gas valves, the thermocouple for the pilot is not producing and is droping out the valve, which will cut off the gas to the pilot and main burner.
So here is the tricky part. The fireplace door is always open. After I finished yesterday, the unit ran for 1.5 hours, and then turned off. Well the initial complaint was that if they take the front logs off, it works fine and doesn't cut off. So the guy takes the logs off yesterday evening, and the unit has worked ever since. The unit is 10 years old, and I don't know if they had the oxygen depletion set ups back then or not. I did not get the model number of the stove, and none of them on the buck sit looks the same on the log setup. The logs don't seem to be changing the shape as the flame, or at least the flame isn't impenging anything other than the top part of the thermocouple. The unit is setup with a remote control. That is all I can think of that may fill in a couple of questions.
I guess what I am down to is perhaps there is an oxygen sensor on this and it is cutting off the unit. I am not sure if those turn off pilot and all or not. Otherwise, it appears to me to be a weak thermocouple.
I guess my questions are -Did they do the oxygen sensors 10 years ago, is the pilot flame adjustable on these small valves, and what would make the unit work without the logs and turn off intermitently with the logs in place?