Heating and cooling systems tend to fail during the hottest and coldest stretches of the year, when they're working hardest and technicians are busiest. Common problems include failed capacitors, worn blower motors, faulty igniters or flame sensors, refrigerant leaks and clogged condensate lines.

Pay attention to rooms that won't reach the set temperature, short cycling where the system turns on and off frequently, unusual noises, burning smells or a sudden jump in your energy bill. Some fixes, like replacing a capacitor, are relatively modest. Major components such as a compressor or heat exchanger can be among the most expensive repairs in a home, and any safety concern with a gas furnace should be handled by a licensed technician.

Changing the air filter regularly and scheduling seasonal tune-ups can catch small issues early. Some homeowners also set aside a repair fund or look into a home warranty. Coverage limits, exclusions and service fees vary widely between plans, so read the contract carefully before deciding whether one fits your situation.