What are the causes if the fuse keeps blowing?
The main causes of frequent fuse blowing are an undersized fuse, a short circuit caused by wire chafing and mechanical resistance straining the motor. The LFT20 draws 10 A on average; at that load the calculated value is 12.5 A, so a 15 A fuse is recommended in practice. Increasing the fuse rating is not a solution; the root cause must be found.
Eliminate the causes in order:
- Fuse rating: The general rule is about 125% of the load. For the LFT20's 10 A average current the calculated value is 12.5 A, and 15 A is used in practice. A fuse below that will blow on the start-up current.
- Mechanical strain: A jammed, rusted or seized mechanism runs the motor at its limit and the current rises. Disconnect the kit and try the lever by hand.
- Short circuit: Look for points where the wire chafes on a sharp sheet edge, the exhaust or a moving part. Use rubber grommets at pass-throughs.
- Damp and oxidation: Moisture inside a connector creates leakage current.
- Wrong fuse position: The fuse must be as close as possible to the source of the wire being protected, that is, to the battery terminal. If it is placed further away, the wire in between is left unprotected.
Do not solve it by fitting a bigger fuse. The fuse protects the wire; raising its rating opens the door to the wire overheating and to fire risk. Since temperatures of 90–105 °C in the engine bay can increase wire resistance by 27–33%, margin must also be left in the cross-section calculation.
Full topic: Converting a tractor hydraulic lever to electronic control