Step 10 · When to Call a Professional

If any of the following conditions are met, cease further DIY attempts and contact a licensed HVAC professional: persistent unusual noises, significant ice buildup that returns after thawing, no power to the unit despite breaker being on, refrigerant leaks (indicated by oily residue on lines or hissing sounds), compressor not running, or any diagnosed electrical component failure you are not qualified to replace.