It seems that after any heavy rain the Master Temp 400 tries to fire up and then quickly shuts gas off to burner. The pattern seems to be that after 3 attempts it quits trying and says service necessary. After I manually turn the unit off and then on again it will again try to start 3 times, and usually will be successful on one of these attempts. I am a bit surprised that rain should be a problem since these units are designed to be outdoors. Does anyone know what the interlock device is that is causing the shutdowns?