Erthal's predecessor, archbishop Emmerich Joseph von Breidbach zu Bürresheim, had introduced some ideas of the Enlightenment, and had been a popular figure.

Directly after the death of archbishop Emmerich Joseph, Friedrich von Erthal, then Domkustos, was charged with reducing the influence of the Enlightenment in the schools and monasteries of the archbishopric.

Erthal suppressed the Carthusian monastery and two nunneries at Mainz and used their revenues to meet the expenses of the university, in which he appointed numerous Protestants and free-thinkers as professors.

The purpose of the punctation was to lower the papal dignity to a merely honorary primacy and to make the pope a primus inter pares, with practically no authority over the territories of the archbishops.

In 1787, he apparently receded from the schismatic position of the Punctation of Ems and applied to Rome for a renewal of his quinquennial faculties and for the approbation of his new coadjutor, Karl Theodor von Dalberg.

The negotiations concerning the reimbursement of Erthal for the loss of his territory west of the Rhine were not yet completed when he died on 25 July 1802, and was succeeded as archbishop by Karl Theodor Anton Maria von Dalberg.