RV Repair: Dometic RM 3604 2 way, dinosaur electronics, flame sensor

Question
Fridge works great on ac, but won't stay lit on gas.  I cleaned it out and found carbon flakes on the burner and ignighter.  The ignighter won't quit sparking after the burner lights, then in a while, the gas shuts off and the red light comes on. The flame looks good till it goes out.  How do you change a board and where is it?  Do I have a flame sensing problem?  Thanks, Alan

Answer
Hi Alan:
The thing that turns off the igniter and keeps the flame going is the flame sensor. If the flame sensor signal is not reaching the board or if the board does not process it correctly the igniter will keep trying to light and in a minute or so the flame goes out. The flame sensor on newer units is part of the igniter. On the older ones it is a seperate sensor sitting just above the flame. It should be positioned in the dark purple color of the flame just above the bright blue section. I have seen very few bad flame sensors and lots of bad boards so the chances are the board is bad. Boards cost $150 or so and flame sensors about $15. It might be worth it to change the sensor first. The board is the black box, about 4"x3", located at the lower left outside under the cover. The best replacement boards are made by a company called Dinosaur Electronics. You can find a local source on the internet. Good luck.
Bill