Make sure the combustion air intake and exhaust are clear outside.
Check the condensate lines and trap for blockages. Water backing up can reduce flow and cause the pressure switch to not make.
Check the pressure switch tubes for blockages.
If nothing is obviously wrong, you'll have to get a manometer to check the draft.
Check the condensate lines and trap for blockages. Water backing up can reduce flow and cause the pressure switch to not make.
Check the pressure switch tubes for blockages.
If nothing is obviously wrong, you'll have to get a manometer to check the draft.