He was a teacher at Zion School, Southwark, Philadelphia from September 1813 to March 1815, when he returned to Germany for a visit. After his return to the United States in 1816, he was licensed as a lay preacher. Heyer worked as a preacher for three years until he was fully ordained in 1820. He spent the next twenty years ministering and establishing churches and Sunday schools in Pennsylvania, Maryland, New York, the mid-western States, and as far west as Missouri.