Hi Mario Farias. I have the MB of North America Electrical trouble shooting manual of this model (350SD-1991 Chasis #126134), and there is no 15 amp. fuse in the circuit neither in the fusebox of my car. There is a 16 amp fuse for the low speed circuit through the pre-resistor, and there is another circuit that goes from the battery to the 40 amp. relay (high speed circuit). I believe the fuse for the high speed circuit is the relay itself. Why would MB designed the low speed circuit with 1.5 mm wire diameter and 2.5 mm diameter for the high speed, as illustrated in the diagram. High speed draw around 23-24 amps. as shown by the instrument. The instrument is a Fluke AC/DC clamp-on ammeter. I think is model 36 but I have to check the correct model #.