Intertherm Furnace Blower Motor Fan & Housing Assembly Tested & Working. From an oil furnace downdraft furnace. Overall height is 15” length 15” x width 9 1/4′. Its easier to change the whole blower than try and replace the motor. MATCH THE WIDTH, MATCH THE BLOWER. TYPICALLY, ALL BLOWERS HAVE THE SAME DIMENSIONS, EXCEPT AS THE BLOWER GETS BIGGER, IT GETS WIDER. MOST ALL BLOWERS HAVE AN AIR OPENING THAT IS 11 1/2 TO 12 INCHES LONG.