How to Solve 5 of the Most Common HVAC Problems

As an HVAC technician, you'll likely encounter many of the same HVAC issues repeatedly. To make the most of your time, it's important to learn how to quickly solve them. Here are solutions to the most common issues you'll see in the field.

1. Dirty Air Filter

Changing a dirty filter is a simple but often overlooked task. A clogged HVAC filter restricts airflow, reducing efficiency and cooling performance. Homeowners should change their HVAC filter monthly, but this is often forgotten. A clogged filter impedes airflow, making the home less cool and allowing allergens to circulate. If a system is performing poorly, the first step should be to check the filter.

2. Evaporator Coils or Dirty Condenser

Dirty coils or fins can reduce airflow and even cause the system to ice over, leading to inefficiency, higher utility bills, and potential component failure.

Cleaning Evaporator Coils

• ​Cleaning coils can take a few hours to do properly.
• ​Commercial coil cleaning solutions are available, but a detergent/water solution can also work.
• ​Use a brush no stiffer than a toothbrush; avoid wire brushes or stiff bristles to prevent damage.
• ​Compressed air can remove dust, but use proper technique to avoid pushing dust further into the coils.
• ​Severe dirt accumulation may require shutting down or partially disassembling the system.

3. Leaking or Low Refrigerant

If the system is still underperforming after checking the filter and coils, check refrigerant levels. Signs of low refrigerant include:

• ​Excessive condensate water around the unit
• ​Frost on copper lines and evaporator coil
• ​Excessive humidity in the home
• ​Poor system performance

If gauges show low refrigerant, isolate and repair leaks before recharging. Leaks can occur anywhere along the refrigerant circuit. To detect leaks:

• ​Use a soapy water mix and look for bubbles, especially around brazed joints, fittings, and valves.
• ​An electronic leak detector with a bendable probe can help find tricky leaks.
• ​Inspect for oil residue around fittings and joints, as this indicates leak locations.

4. Malfunctioning Thermostat

The thermostat controls the entire system. If the thermostat is set correctly but the temperature is off, try resetting it. Next steps:

• ​Ensure the thermostat has power.
• ​Shut off power, remove the cover, and inspect wiring for loose connections, corrosion, or damage.
• ​Use a multimeter to check wiring continuity.
• ​Troubleshooting may vary, especially with programmable thermostats.

5. Tripped Breaker or Blown Fuse

HVAC systems use high current and have high-amperage breakers. If the unit isn't functioning, a tripped breaker or blown fuse may be the cause. A breaker usually trips for a reason, such as a power surge or lightning strike.

Steps to address this:

• ​Turn the system OFF at the thermostat.
• ​Flip the breaker ON and see if it trips again.
• ​Wait 30 minutes before turning the thermostat back ON to allow the internal breaker to reset.
• ​If the breaker trips again, do not try a second time.

Possible causes for repeated tripping:

• ​Short in an electrical load
• ​Short to ground in an electrical load or wiring
• ​Seized compressor
• ​Wiring problems (dead short, corrosion, loose connection, animal or insect damage)

Diagnosing and repairing these issues requires advanced troubleshooting skills and safety precautions due to high voltages.