In this study, an open-loop air source heat pump drying system using R134a refrigerant was developed and investigated experimentally in the laboratory at varied ambient temperatures and fan speeds. The ambient temperatures were controlled and examined from 20 °C to -10 °C at increments of 10 °C and the condenser and evaporator fan speeds were synchronised and examined at 60%, 80, 90%, and 100% of the full speed. The results show that both the change in fan speed and the ambient temperatures play a significant role in the operating conditions of an open-loop heat pump system. Increasing the condenser fan speed increased the heat rejection to the sink to a peak at 90% fan speed while increasing the evaporator fan speed increased the thermal energy input from the heat source. As a result, the compression ratio decreased and the refrigerant mass flow rate increased. Due to the lower ambient temperature, the discharge pressure was 1.42 times lower than the suction pressure. Furthermore, due to the refrigerant density significantly dropping with the decrease in ambient temperature, the refrigerant mass flow rate was low, which reduced the efficiency of the heat pump drying system.