No heat whole home. Customer believed system was low on refrigerant based on outdoor coil having previously severely frozen over. Upon inspection found system to be properly charge. Based on symptoms customer described tested defrost. Defrost board did not send board into defrost. Also found defrost sensor open. Jumped sensor out and defrost still did not activate. Coil was freezing and sensor should have been closed. Board and sensor have failed. Customer approved repairs to be completed at a later date as parts are not currently available. Estimated delivery time was 3-5 days.