Is there such a thing as a weak fuse?

Yes, a weak fuse can refer to a fuse that has a lower current rating than necessary for the circuit it protects, resulting in frequent blows even under normal operating conditions. Additionally, a fuse can be deemed "weak" if it is old, corroded, or damaged, which may cause it to fail prematurely. Such fuses can lead to unreliable circuit protection and potential safety hazards. It's important to use fuses that are appropriately rated for their specific applications.