The objective of this study was to investigate the impact of the electronic expansion valve opening in an automotive heat pump system with an economizer on the system winter heating performance and frost-related characteristics. The experiments were conducted at a temperature of -10°C during the winter months. The adjustment of the opening degrees of the main and complementary electronic expansion valve was implemented to facilitate an analysis of the heating performance parameters and the alterations in frost formation and melting. The findings demonstrated that a diminution in the main circuit electronic expansion valve opening from 40% to 24% resulted in an augmentation of the exhaust gas temperature by 12.24°C, accompanied by a maximum heat production of 2.837 kW and a COP of 1.99. In the low pressure makeup mode, an increase in the makeup electronic valve opening from 8% to 15% resulted in a 7.27°C decrease in the exhaust gas temperature. Concurrently, the maximum heat production and the COP reached 2.851 kW and 2, respectively. In the medium pressure makeup mode, an increase in the makeup electronic valve opening from 8% to 20% resulted in a 9.4°C reduction in the exhaust temperature. This adjustment resulted in a maximum heat production of 3.235 kW and a COP of 1.96. In consideration of the subject of frost-related phenomena, the following observations were made: the duration required to execute frosting in the no-makeup gas, low pressure makeup gas, and medium pressure makeup gas modes was 82 minutes, 90 minutes, and 95 minutes, respectively. The duration required for frost melting was determined to be 5 minutes and 20 seconds, 4 minutes and 30 seconds, and 3 minutes, and 56 seconds, respectively. These findings offer significant insights in-to the optimization of automotive heat pump systems during winter operations.