A modern 30A fuse is NOT suitable and is a good way to melt wiring.
The short version is that the Lucas fuses originally fitted were rated differently and a 15A modern fuse is a closer equivalent. To confirm you can compare the internal fuse wire/metal size of an original Lucas vs modern fuse. If you look at a 30a modern fuse the fuse material is very obviously a larger diameter and therefore takes a lot higher current before blowing (very bad idea).
If you want more information there are plenty of discussions online about it.
Fit a 15A fuse.
The fuse is blowing because you have a fault. I am currently rewiring a vehicle because someone had decided to add an electric fan as well as indicators using the original trafficator supply wiring. They obviously had fuses blowing so what did they do? Bypass the fuse. The result was of course melted wiring and a melted terminal block. Increasing the fuse capacity like you have done would've ended with a similar result.
Edited by 68+86auto, 11 December 2023 - 02:12 AM.