F 700 speedometer

[bmulker1]

I am working on a 1991 ford F 700 dump truck trying to repair the speedometer. The signal comes from a variable relucter mounted on the transmission. According to the manual there is either a fuse or a non-re settable circuit breaker in the circuit. I can find no fuse in the box, Does anyone know where this item would be physically located?
Thanx!