Many homeowners are not comfortable tackling HVAC problems, and often the necessary equipment is prohibitively expensive. Even so, there are some simple tasks homeowners can perform to figure out why their HVAC unit isn't working. At best these steps may eliminate the need to schedule a technician, and if not, at least you've narrowed down the problem.
Check Your Air Filter
The number one thing homeowners can do to ensure the functionality and longevity of their HVAC system is to change the air filter regularly. A dirty air filter hampers air flow causing the unit to work that much harder, and if there isn't enough air moving over the evaporator coil, it can freeze over into a solid block of ice (That's solid ice surrounding the evaporator coil in the photo!).
HVAC professionals I've spoken with say that if allergens are not a problem, use a basic, 30-day air filter and change it every month. Be especially mindful during home renovations when the air may have higher amounts of dust and particles.
Check the Fuse
The compressor unit located outside a home will have a dedicated fuse or fuses to protect against electrical malfunctions and damage. Over time these fuses can go bad. Much more likely, the fuse did its job and was blown when the electrical current exceeded safe levels. Often a blown fuse is obvious because of the flash marks in and around the window. If the fuse doesn't have a window, a multimeter (set to Ohms) can be used to check the continuity of the fuse and the fuse box.
Air Temperature Change
The air supply and return should have a temperature differential of 18° - 20° at the evaporator coil, and this can be measured with a simple, digital cooking thermometer. If the temperature difference is less, that may indicated a dirty coil which can be cleaned by carefully vacuuming the coil.
Inspect and Clean the Drain Line
The evaporator coil and warm air create condensation which is carried away through the drain line. This drain can become clogged, especially during winter months when the drain isn't very active. If that's the case, water will backup and either trip an auto-shutoff or slowly rust the unit.
It's good practice to clean out the pump reservoir and also pour 1/2 cup of bleach through the drain line (most have a removable cap for access) annually. However, a defective pump or oversized trap can also be the culprit.
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Ethan Hagan is the primary editor at One Project Closer. Ethan spends most of his days shadowing real contractors on actual job sites and most of his nights writing about it. To see what I mean, check out their expert guides like How to Build a Deck. If learning and interacting with pro contractors sounds like something you’d enjoy, sign up for OPC email updates.