I have an intermittent problem. On my Rheem (ROBC-112QBGA) oil furnace at times the blower kicks off prior to the burner shutting. I believe the thermostat gets satisfied and is not triggering the burner to quit but begins the timing sequence of the blower. Hence, the blower times out and the fire box immediately heats up to 170 degrees and the limit switch (thankfully) shuts the burner off. I replaced the fan relay sequencer but the intermittent problem returned. After the thermostat is satisfied, what controls the burner shut down? Is it the Fan Timer Control? Thanks