Dynamica Mini 40 producing 8v

[terah]

We have a dynamica mini 40 on board our new to us boat but have not used it much due to lack of need and a separate issue with the amount of noise it makes.

Today we realised our main engine alternator was not working so we started up the generator to top the batteries up.

The generator ran fine for about an hour, then I started the A/C. At that point the voltage dropped to about 140v. I stopped the A/C straight away and the output stayed at 140v for a few mins, then dropped to 8v.

Any ideas?

[terah]

Circuit breaker and accessible (external) fuse are fine, but on opening up the wiring box found this:



Fuse had blown out of the holder. It is a little corroded but can make out F10A500V, with what appears to be '1/6' before the F. Is that some rating of how fast it should blow?

So hopefully this is the culprit, but out of interest what is this fuse for and why would it blow before the main one?

Thanks.