Step 4 · Inspect Refrigerant Lines

Locate the copper refrigerant lines connecting the outdoor condenser unit to the indoor air handler. One line is larger (the suction line) and the other is smaller (the liquid line). Check both lines for any oily residue, which could indicate a refrigerant leak. Also, look for any signs of physical damage, kinks, or corrosion. The larger suction line should be insulated; ensure the insulation is intact and not degraded. If you see frost or ice on the lines, it typically indicates an airflow problem or a low refrigerant charge, and you should consult a professional.