Before calling a technician for a no AC Call:
Step 1. Make sure the Breakers in the Electrical Box for any Heating and Air Conditioning Equipment are on.
Step 2. Make sure that any emergency shutoff switches are on and that if there is a led light in the furnace, that it is on.
Step 3. Make sure that all filters are clean.
Step 4. If you thermostat has batteries in it, make sure to replace them with fresh batteries and that there is no corrosion on the battery terminals.
Step 5. Sometimes programmable thermostats will revert back to a program which may be at a higher temperature unless you press the HOLD button. Make sure that the thermostat is definitely set lower than what it is currently reading in the house and that the mode is set to cool.
Step 6. When the thermostat is calling for cooling and the fan is running, is the outdoor unit’s fan and compressor running? The more info you can give the technician the better even if you at least can see the outdoor units fan running but are not sure whether the compresser is running.
Step 7. At the outdoor unit, is the smaller copper line warm and the larger copper line cool to the touch? These are the lines that connect the indoor unit to the outdoor unit. This would at least tell you if the compressor is running as you will have a temperature diferrence between the two.
Step 8. See if the indoor fan will at least turn on at the thermostat when you select fan on instead of fan auto. If the fan turns on then at least you know that you have power and that the fan motor works.
Step 9. If you notice that when the thermostat is calling for cooling, the outside unit is running but there is no air flow at the registers in the house, turn the AC off at the thermostat or breakers to avoid any further damage to the AC units or the building and to stop the Evaporator Coil from freezing.
Step 10. If you notice that the indoor fan runs but the outdoor unit is not running, you could check to see if a fuse is blown at the outdoor disconnect. Not every building will have outdoor fusible disconnects. Some buildings may have non fusible disconnects where nothing may need to be replaced. It is possible for a bottle fuse to blow over time from just being old, a one time voltage spike or reduction in voltage from the electrical company’s transformer at the pole or some other abnormallity such as lightening. You could try replacing the fuse after you turn the power off to the unit and all power switches and breakers to all AC equipment is in the off position. Bottle fuses can be found at any local hardware store. Be sure to install the correct fuse for the outdoor unit. On the outdoor unit’s rating plate it will same MAX AMPs or MAX FUSE. Make sure each of your fuses are the same as the max rating on the Outdor unit. If the unit says 30 AMP MAX FUSE then replace the fuses with 2 of the same size 30 amp fuses.