While camping this past week, we were able to stay warm but it seemed that the furnace was not putting out as much air volume or as warm air as recall from past trips. The furnace started fine and ran until the thermostat shut it off upon reaching temperature. I plan to take the inside cover off the furnace tomorrow to see it I can detect anything. The floor grates have no adjustment and are full open. I think it is only a one speed blower. I read the library furnace notes but didn't see anything that jumped out at me.