Upon arrival homeowner played a recording of a sound issue with outdoor unit. Tested and ran system at 100% heating mode via thermostat. Allowed system to run for 5 to 10 minutes and checked noise level on outdoor unit, system ran normally with no issues. Informed homeowner noise issue possibly came from a tree branch or rock possibly stuck inside fan when running causing noise issue. Informed homeowner to keep an eye out for noise issue and contact us if problem still occurs. Also showed homeowner how to turn fan on continuously for system instead of circulate. System is operational at this time.