reekonator

Hello people, My furnace is a 6 year old Keeprite 60,000 btu gas furnace. Recently i have been having a problem with condensation building up in the tube that goes from the exhaust blower to the vacuum diaphram switch. When this happens it shuts the gas valve off prematurley. If I take the tube off and empty the water out of it and also the switch the furnace runs fine until the same thing happens again. Any ideas why this is happening all of a sudden ?. Any replies would be great. Reekonator