My Coleman Evcon furnace will not heat. I took off the cover and saw a red light flash three times indicating pressure switch failed to close. I blew into both ends of the rubber tube. I noticed a click as I blew in the direction of the pressure switch and another click as I ceased blowing. Other than that, I am out of ideas. Thanks.

Make sure the rubber hose doesn`t have any holes or cracks and that it fits tight on both end connections

Thanks for responding wmproop. The hose is in good shape and the connections are tight.

Take the vent motor out and check for a blockage, birds or dirt.