To repair a Fedders air conditioner, first try removing and cleaning the filter, and then try resetting the breaker or resetting the unit. Refer to the unit's user manual for fixes specific to the model, and contact a qualified repair technician for repairs on the inside of the appliance.
If the Fedders air conditioner is not cooling the room sufficiently, turn the unit off using the control knob, and open the front panel. Remove the filter before thoroughly cleaning it with warm, soapy water. Wait until it is completely dry before returning the filter to its place. Other fixes to try include replacing the filter with a new one, cleaning the fins of the coil with a vacuum, using a rag to wipe the inside of the unit and lubricating the motor per the model's instructions in the user manual.
If the unit does not start, turn the circuit breaker switch off and on again, and check the outlet to ensure that it is working properly. Unplug the unit's cord, and plug it in again after several seconds. If the air conditioner's light is off, you may need to replace the fuse. If the light is on but the unit is still not working, the unit may need more in-depth professional repairs.