Rheem thermostats such as the 500 series or 400 series include features for controlling temperatures for Rheem residential and commercial HVAC (Heating, Ventilation and Air Conditioning) units. With touch screen displays, programmable settings and humidity control features, a few troubleshooting guidelines may ensure that your unit maximizes efficiency.

Step 1

Check the wiring on your Rheem thermostat if the indoor unit is not detected by the network. The "Check System Fault" message appears on your thermostat if the unit is not detected by the network.

Step 2

Turn on your furnace or air conditioner if your thermostat is still not detecting a device on the network. Your thermostat begins searching for the devices, and display the "found' message when it detects a furnace or air conditioner. If after five minutes no devices are found, check your equipment. Check the circuit breakers inside an electrical panel in basement, attic or electrical room depending on your house. Turn the circuit breakers off and then turn them back on to reset them.

Step 3

Remove the batteries from your Rheem thermostat if you see a low battery warning on the screen. Insert fresh new alkaline batteries into the battery compartment. Some digital Rheem thermostats do not use batteries, so refer to your manual if you are unsure how your thermostat is powered.

Step 4

Check the system operation on your thermostat. Press the "SYSTEM" button continuously until "Heat" is displayed if your furnace is not producing heat. Press the up arrow button to adjust the thermostat setting to at least one degree higher than the room temperature displayed on the screen. If your heating unit has additional stages, adjust the temperature to 3 degrees Fahrenheit above the actual temperature.

Step 5

Press the "SYSTEM" button continuously until "Cool" is displayed if your air conditioner is not blowing cool air. Press the down arrow button to adjust the temperature setting below the room temperature displayed on your thermostat. If your cooling unit has additional stages, adjust the temperature to three degrees Fahrenheit below the actual temperature.

Step 6

Press the "FAN" button repeatedly until "Fan On" is displayed if you do not hear the fan on your unit. Select "Fan Circ" or "Fan Auto" depending on your preference.