Even with proper design, installation, and maintenance, HVAC systems can still fail due to a variety of factors such as age, wear and tear, and environmental conditions. As an HVAC technician, it's important to be knowledgeable about common system failures and repair procedures to quickly diagnose and solve problems.

Some common HVAC system failures include:

1. Compressor failure: The compressor is the heart of an HVAC system, and when it fails, the entire system is affected. Signs of compressor failure include unusual noises, reduced cooling or heating performance, and high energy bills. Repair procedures include replacing the compressor or the entire system if necessary.
2. Refrigerant leaks: Leaks can occur due to faulty connections, corrosion, or physical damage to the refrigerant lines. Symptoms of refrigerant leaks include reduced cooling or heating performance, ice buildup on the coils, and hissing noises. Repair procedures include identifying and repairing the leak, replacing damaged lines or components, and recharging the refrigerant.
3. Electrical failures: Electrical problems can cause a variety of issues such as blown fuses, tripped breakers, and failed capacitors. Symptoms of electrical failures include the system not turning on, unusual noises, and erratic operation. Repair procedures include testing the electrical components, replacing damaged parts, and ensuring proper connections.
4. Clogged air filters: Dirty air filters can reduce airflow, strain the system, and cause premature failure of components. Symptoms of clogged air filters include reduced cooling or heating performance and increased energy bills. Repair procedures include replacing the air filters and ensuring proper maintenance schedules are in place.

In addition to these common failures, HVAC systems can also experience problems such as ductwork leaks, thermostat malfunctions, and blower motor failures. As an HVAC technician, it's important to be knowledgeable about these issues and their respective repair procedures to provide efficient and effective service to clients.