The Freightliner tow fuses are usually at the rear on the driver side.  Usually found in one of two spots... in the electric bay behind a panel that is screwed on to the wall, or (as in mine) in my side-mounted radiator bay.  Not sure which engine you have on yours, but if you have the side radiator then you need to unscrew that panel (2 screws on side in next bay, 2 underneath) and prop the panel up.  My fuses were at the right, at the very back of the coach.
Others have found them behind the power bay panel... look for 6 screws holding a panel to a wall.
Here's a thread with pictures...
clicky