fuse rating for blade fuse upgrade

I'm in the process of upgrading the fuse box on my 25 year old 90 getting fed up with bad connections, the brake light and flasher circuit I changed to a blade earlier this year. I've got all the bits from Vehicle Wiring Products but when ordering from them on their website the blade fuse ratings show double the marked rating for the blow rating. I have read conflicting views on the rating for the old glass fuses some say the marked rating is the blow rating and some say it's the continuous ampage that's marked. Must be lots of people on the site have done this job and would like to know what fuses they used. Want to get this right before I start.
Alan.

a 30A fuse can cope with 30A of current at constant draw. Blow rate depends on current draw and length of time, e.g. at 40A through a 30A fuse it may take a minute to blow, but, at 80A through a 30A fuse it is more likely to blow in under a second.

However, there is unlikely to be anything that delicate on your landy that will have major issues with over current related faults.

stick a meter in each one at full load and see whats really needed

When I swapped mine over from glass to blade type I just used the same ratting that came out. Never had a problem with it.

If i remember right there is a difference
One will blow at its rating the other will take the current but blow a twice its rating

I was hoping to hear that someone used the same rating and everythings OK,
though it seems the lowest rating I can find is 3 amp to replace the 2.5 glass and I was going to use 7.5 to replace the 8 amp glass, the problem one seems to be what to use for the 12 amp glass, I was just going to use a 10 amp and see how it went, otherwise It would have to be 15 amp and I'm not too sure about that.

Fuse are marked with the current that they will continuously pass (at a standard temperature) without blowing, known as the continuous rating. It is good practice not to allow the continuous current to exceed 75% of the fuse's rated value to accommodate momentary current surges that might cause the fuse to fatigue over time or blow unecesarily (nuisance blow).

Blow rating

In simplified terms this is the current rating at which the fuse will blow. Most fuses have a blow rating around twice that of the marked continuous rating. So a 5A continuously rated fuse will have a blow rating of 10A.

Some older style fuses may still be marked with the blow rating rather than the continuous rating so care should be taken when replacing an older style fuse with a modern one that the ratings are understood and the correct fuse used.

landie3 said:

I was hoping to hear that someone used the same rating and everythings OK,
though it seems the lowest rating I can find is 3 amp to replace the 2.5 glass and I was going to use 7.5 to replace the 8 amp glass, the problem one seems to be what to use for the 12 amp glass, I was just going to use a 10 amp and see how it went, otherwise It would have to be 15 amp and I'm not too sure about that.

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Yep, Go lower with the ratings if you have to. Again that's what I did and none of them blew.

I've just ordered some 1 amp and 2 amp blade fuses from ebay so I can cover the 2.5 glass, so I'm going to start by halving the blade fuse rate and see how it goes, the 12 amp is still the problem so I'll just try a 7.5 blade in that circuit I think the 5 amp may be too low.
Alan.

landie3 said:

I've just ordered some 1 amp and 2 amp blade fuses from ebay so I can cover the 2.5 glass, so I'm going to start by halving the blade fuse rate and see how it goes, the 12 amp is still the problem so I'll just try a 7.5 blade in that circuit I think the 5 amp may be too low.
Alan.

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what circuit has 2.5 amp glass protecting it?

That's the left and right side light circuits.

sidelights are 10w a side, so less than an amp.... but you need some spare amps for when you have a trailer on

this is form the 300tdi, dont think wiring changed that much, but should give you a guide.