keeps blowing out when replacing it with a new one.
fuse#41 cigarette lighter/obd II diagnostic connector on 2003 Ford Expedition
Check the cigarette lighters, people throw change in the ash trays and coins and other debris get into the sockets and short the element.
nothing found lighter?
According to the wiring diagram; That is the only 2 things wired to that fuse. Can you unplug the cigar lighter power connector to ensure that it is not shorted, or maybe some add on has been wired into that circuit causing the problem. The only other idea is maybe the wire is shorted somewhere. The lt blu/wht wire to the DLC is the B+ wire. If all else fails cut the wire and add another B+ to be able to scan your vehicle. My tools have an auxillary adapter to be able to bypass the DLC power and power the scan tool.
The socket sometimes gets slightly damaged and the positive connection will be touching the outer housing. Usually all it needs is pulled away from the outer housing. You have to look really close at the two fingers that extend from the bottom of the socket, they should not be touching the housing.