Horizontally mounted compressors offer the advantage of reduced height in central air-conditioning units but prove difficult to produce economically due to costs associated with the manufacture of acceptable lubrication systems for the compressors. This study develops an effective, affordable oil pump for use on a horizontal compressor. Concepts are proven through testing of prototype assemblies. Test results drive modifications for future prototypes, and prototypes demonstrating adequate performance are modified for ease of manufacture. Research in this study proves that the most suitable design results from a modification of a rotating vane pump. The pump’s modifications enable it to pump oil in the same direction, regardless of the direction of shaft rotation and to prime itself when totally dry of oil. However, extensive use of horizontal compressors hinges upon the development of a satisfactory suspension system.