In 1819, Wieselgren went through a spiritual change of heart, and after a time of worry and sorrow over what he felt was sinful, he asked God for light and peace.

On 24 April 24 1819, they all signed an agreement which stated, among other things, "We also renounce, though separately and without burdening the conscience of others, all use of spirituous beverages which are not beneficial to health and which may become corrupting through habit."

He founded the Västerstad temperance society there, which, after a year's work, held a celebration at which 100 farmers took a vow of sobriety.

When Wieselgren moved from Västerstad after 15 years to take up the post of vicar in Helsingborg, it was said of him that "he had received the parish neglected like a wilderness, but left it like a well-tended herb garden".

[7] During the first decades of the 19th century, the consumption of spirits increased considerably in Sweden as a result of domestic distilling.

[8] In the late 1820s, the priest Carl Emanuel Bexell [sv] had formed one of Sweden's first temperance societies in Rydaholm, Småland, and subsequently several others.

Wieselgren became a prominent traveling speaker for the Svenska nykterhetssällskapet (the Swedish Temperance Society).

[11] On the occasion of the inauguration of the Western Main Line on 4–5 November 1862 in Gothenburg, Charles XV once wanted to toast with him, but even then he would not pour wine into his goblet.

This Wieselgren family comes from Erengislegården (Gunnarås) in Västra Torsås parish in Kronoberg County, where the progenitor Måns Olufsson lived during the 17th century.