Rosanky Ac service Upon my arrival, I checked into the concerns of the system being frozen outside. Performing my diagnostics. I found that the defrost control board has faulted preventing the system from going into defrost in low ambient temperatures. While on site, I did defrost the system in cooling mode and then checked pressures and heating mode to verify that we had adequate refrigerant levels in the system. I spoke with the customer about my concerns and they approved a repair and a return will be scheduled through the office.