Why Does My Fuse Keep Blowing?

A fuse that opens repeatedly indicates a problem to diagnose. The cause may be a short, sustained overload, high startup current, poor holder contact or the wrong specified replacement. A one-time opening also deserves investigation, especially when there was heat or smoke.

A safe sequence

1. Turn off power and identify the circuit from its manual or diagram. For mains equipment, high-voltage appliances or an unfamiliar battery system, use qualified service.
2. Confirm the replacement’s ampere, voltage, time characteristic, interrupt rating and size against the equipment specification.
3. Inspect the holder and wiring. Isolate disconnected loads and measure current only with appropriately rated tools and training.
4. Repair the actual fault, then fit the specified fuse and test.

Do not automatically switch to a time-delay fuse or calculate load × 1.25 to justify a larger one. Either change alters the design’s protection. Do not bypass the fuse while searching for a fault.

Reference material

• Fuse technical reference
• Wire technical reference