Fuse Blowing
The fuse breaking the circuit as a result of the current in the line exceeding its rating. A single blow is an event, but a repeated blow is a symptom and its cause must be found. There are three main sources: motor current rising because of mechanical binding, a short circuit in the wiring, and a wrongly chosen fuse rating.
Narrow down the diagnosis in order:
- Is the fuse rating correct: was it chosen according to the rule of roughly 125% of the continuous current? For the LFT20, against a 10 A average current, 15 A is recommended in practice.
- Is there mechanical binding: move the cable and the lever by hand. A mechanism under strain brings the motor close to stall current and blows the fuse.
- Is there a short circuit: check that the cables are not chafed on sheet metal edges and that the connectors have not got wet. With the system de-energised, measure the resistance between the positive line and the chassis.
- When does it blow: if it blows only at start-up, moving to a time-delay type fuse may be appropriate; if it blows continuously, the fault is mechanical or electrical.
The one thing that must not be done is clear: fitting a fuse of a higher rating. This disables the only element protecting the cable. On products with current protection such as the LFT54, the protection usually acts before the fuse; if the fuse is blowing, the problem is in the line.
The context where this term is used: Converting a tractor hydraulic lever to electronic control