Founded in the mid-1920s by brothers Richard and Donald Rheem, the Rheem Manufacturing Co. is a well known producer of residential heating and cooling systems. Rheem furnaces contain an internal limit switch that regulates the fan and helps prevent the unit from overheating. If the fan in your furnace runs continuously or turns off and on too frequently, you may need to adjust or replace the limit switch. Finding the limit switch in a Rheem furnace takes just seconds.
Remove the top access panel on the front of the Rheem furnace. Hold the sides of the panel while lifting it up and toward you. Set the removed panel aside.
Examine the exposed furnace components to find the plenum, or main duct junction, on the furnace's upper housing; the plenum is a small metal box that is secured to the top of the furnace cabinet with several sheet metal screws.
Look for the fan limit switch, which is mounted to the side of the furnace plenum. Look for a flat, round component that is labeled "Fan Limit."