The last thing you want during a nasty heat wave is to wait for days until an HVAC technician or your local AC repairs person shows up to see why your system might have failed. Moreover, not everyone will welcome the standard price of these repairs, which tend to figure in hundreds of dollars.
Instead, you could give your inner electrician a little pep talk, invest approximately $50 in some spare parts, set aside around two hours for a little DIY home maintenance, and spare yourself the hassle. In fact, many experts like the residential heating system technologists affiliated with the Department of Energy encourage homeowners to nurture some basic maintenance and repair skills regarding their HVAC equipment.
As an added benefit, if these simple self-reliant solutions turn out to not be enough to fix your problem, you will have at least covered your general bases. Therefore, when you decide to call in the pros to take a look, they can skip the generic stuff and focus on finding what the elusive issue is.
Check your furnace before anything else
Set your thermostat into air conditioning mode, lower the temperature, and wait. If the furnace fan starts up, everything is fine here. If not, reset the furnace circuit breaker. If that does not fix it, call a professional, such as Tek Climate Heating & Air Conditioning, because the following DIY tactics will not be effective here.
People often go straight to fixing the AC itself and skip the furnace or air handler unit completely. Do not be those people. Check the possible root of the problem – the furnace – right off the bat.
Also check the external condensing unit to see if the compressor and the fan are working. In case they are not, the steps below will help fix them.
Figure out your spare parts requirements
For any of these DIY fixes, chances are you will need a spare part or two. The parts that fail most often, especially in an air conditioning unit that is more than five years old, are the start capacitor (aka run capacitor) and the contactor (aka the relay).
Luckily, they are also rather inexpensive. Note down the serial number, make, and model from the nameplate on the condenser unit and visit an appliance store or a furnace dealer, or look online.
If you are not entirely sure what those are and where in your device to find them, you can read up on the basic anatomy of an AC at this link.
Check the essential trinity: registers, filters, coils
If you are not getting any cool air from your unit, check to see if all the registers in the house are open. Ascertain whether the furnace filter is properly clean. If it is clogged, or if the registers are closed, the airflow is obstructed. If, however, everything is fine and you are still dying for a cold breeze, you likely need to de-ice the A-coil.
Switch the thermostat from “cool” to “off” and the fan from “auto” to “on”. Let the blower run for a minimum of half an hour, then turn the AC back on for a test drive. If it works fine over the next 12 hours, problem solved!
Pop outside and take a look at the condenser coils as well, since they get clogged too. This overheats and shuts down the compressor. Switch the furnace circuit breakers and AC service in the main electrical panel to “off”, the furnace/air handler power switch too, and clean the condenser coils thoroughly.
Inspect the fuses and the access panel
A blown fuse means that a part inside the condensing unit has failed, so simply replacing the fuse will not fix the situation. You need to address the situation in the access panel before you install new fuses and start the AC again. If you are not sure how to go about replacing the fuses, check out this helpful article: https://dengarden.com/appliances/How-to-Replace-Air-Conditioning-Fuses
Follow the electrical conduit from your home to the access panel and switch off the power. Unscrew and remove the cover, and take a moment to check for signs of chewing on wires, connectors, and insulation – you may have a rodent infestation. Look for their nests. Should you find them, replace the start capacitor.
To avoid injury, you have to discharge stored energy first. Touch an insulated screwdriver between the “H” (HERM), “C” (COMMON), and “F” (FAN) terminals to create a short. Remove the capacitor from the retaining bracket and clean out the nest.
Pluck one wire at a time with needle-nose pliers and snap it tightly onto the new capacitor. Before you disconnect anything, take a photo for later reference. If you are not sure that you can safely handle electrical repairs, call a pro.