Is it OK to replace 3 amp fuse with 5 amp fuse?

No, it is not advisable to replace a 3 amp fuse with a 5 amp fuse. Fuses are designed to protect electrical circuits by breaking the connection when the current exceeds a certain threshold. Using a higher-rated fuse may allow too much current to pass through, potentially leading to overheating, equipment damage, or even fire hazards. Always replace a fuse with one that matches the original rating.