I am having a problem with a component of my natural gas furnace rattling. I have a Laars Mini-Therm II heater with an Armstrong motor attached to one of the gas lines. I believe the rattle is coming from somewhere around the motor. The rattle comes and goes for a few hours at a time (very annoying). If I shut the valve on the gas line the rattle stops. My guess is that the pressure of the gas moving through the pipe is causing a rattle somewhere. Does anyone have an idea as to how I could fix the problem.