RATTLE IN THE FURNACE. I WAS ABLE TO FIND THE ISSUE AS TO WHY THE FURNACE WAS RATTTLING. I WAS ABLE TO ADJUST THE HEAT EXCHANGER TO ELIMINATE THE NOISE. ALSO THE RATTLE THE HOMEOWNER WAS HEARING DOWNSTAIRS WAS THE CEILING REGISTER. I WAS ABLE TO ADJUST THE REGISTER TO ELIMINATE THE NOISE. THE SYSTEM IS RUNNING QUIET NOW .