Check the gas line first. Smell and inspect the propane or natural gas supply line going to the Ritetemp space heater. The heater can't produce heat if there is no fuel to the unit. This is also a fire hazard. Look over the gas supply line carefully with a flashlight for any cracks, remaining alert for the odor of gas. Wet the line with soapy water using a bottle sprayer. Any leaks will bubble. Replace the line if necessary.
Clean the "cabin," which is the on the bottom of the heater. Unfasten the panel screws with a screwdriver to access the cabin. Remove any debris with a brush and damp cloth. Debris can build up and cause the unit to run less efficiently. It will also produce a foul and possibly noxious odor to emanate from the Ritetemp.
Inspect the heater's blower and fan assembly. Look for obstructions preventing the fan from turning, and look around the blower for corrosion or burn marks. If either exist, have it serviced by a professional. Test the voltage of the blower with a multimeter. If the blower does not draw current, it is probably bad. This should be replaced by a knowledgeable service technician.