Total cross sections for collisions of He(1S) atoms with H2CO molecules at interstellar temperatures (18–120 K) have been calculated using the L2 R-matrix method developed previously. Using 13 slightly nonorthogonal radial basis functions, excellent agreement has generally been obtained with an earlier close-coupled study. However, in two crucial regions (32.7 and 47.7 K) where strong resonances had been reported, we find that the cross sections are smooth. The accuracy of the present calculations were checked at intervals using the de Vogelaere method with parameters set very tightly. Strong resonances in the 20.2 K region were however found and characterized as being of Feshbach (compound state) type, with the He atom lying in the potential well near the O atom of formaldehyde. Similar resonances in the 127 K region are also predicted. Consequently the state-to-state rate constants, upon which the collision pump mechanism for the cooling of the k doublets of formaldehyde depends, now need to be recomputed using the new values for the cross sections. This series of studies shows that the use of slightly nonorthogonal radial basis functions—and which as a result possess arbitrary derivatives at the R-matrix boundary—is the key to the reliable application of this very stable and versatile method to molecular collision problems. [ABSTRACT FROM AUTHOR]