Some DIY air conditioner repairs include cleaning the furnace filters and condenser coils, opening all the registers, deicing the A-coil, and replacing the filters. Others include checking and replace fuses, replacing damaged wires and connectors in the access panel, and replacing the condenser fan motor, contactor and capacitor.
Begin repairing an air conditioner by setting its thermostat to the cool mode. The furnace fan should start working. If it doesn't, reset the circuit breaker of the furnace. If the fan still does not start, contact a professional.
Switch off power to the air conditioner. Undo the thermostat's cover, remove the "Y" terminal wire, and touch it to the R terminal's exposed end for a couple of minutes. If the unit turns on, it indicates a faulty thermostat that needs replacement.
If the unit does not supply cold air, switch off the power supply, clean the coils of the condenser, clean or replace the furnace filters, and open any closed registers. If the airflow is still not proper, turn off the thermostat, set the fan switch to "On," and allow the blower to function for at least 30 minutes to remove ice built-up from the A-coil.
If the air conditioner does not cool properly in the next 12 hours, use an Ohm meter to check the disconnect block's fuses. If the reading is zero, infinity or negative, it indicates a blown fuse that needs replacement. In addition, replace the capacitor and contactor as problems with these cause the fuses to blow. The capacitor is located in the access panel and the contactor in the condenser. Note their existing wiring to make replacement easy.