Here's a question: WHY would anyone go to the tremendous trouble and cost of replacing the factory-fitted main fuse box, just so they can use spade fuses in place of traditional glass fuses?
Would I be correct in thinking that people are getting a lot of blown fuses? And that the faffing about involved in sending away for older-type one inch glass fuses, plus the relative ease with which inserting spade fuses makes all that cost and effort of doing the replacement worthwhile?
If these are your reasons, then you've got far bigger problems than seeking advice of getting and fitting a new fuse box. You MUST investigate why those fuses are blowing! Never, never ever, replace a blown fuse and think "job done"; you may have an intermittent electrical short that could lead to a fire in your 30+ something years old Landy. Indeed, I think I'm correct in saying that electrical fires are relatively common in old Land Rovers.
Ok, I've not had to change a single fuse in my 1987 Ninety for as far back as I can remember. In fact, not since I discovered the difference between "continuous" and "blow" fuse ratings, which led to me fitting the correct Amperage fuses and writing my first post on here.
Not one single blown fuse in many years.
So, how come I rediscovered this thread? Well, it popped up when I saw that a certain company had an "offer" on for 1" glass fuses, and I needed to remind myself (Google) what Amp rating fuses I might want to put into my spare bulbs and fuses box. I could only dimly recall that the ratings were NOT "what it says on the tin" (or fuse box cover), so to speak.
If you don't believe me, try searching Rimmer Bros website for a 35A 1" glass fuse. It says, "Fuse - 35 amp 17 amp Continuous - Glass type ... GFS3035 - Genuine MG Rover". Ok, it might have been more clearly written, but it is important you're aware of this, particularly if you're looking at blade vs glass fuse ratings. Fitting too small an Amperage fuse -- one that is designed to "blow" at an Amperage close to your "continuous" Amps -- this will cause that blade fuse to heat up, and while it might not blow for several months, that ain't a good thing. Things might be glowing behind your fuse box cover.
Apparently it all goes back to how the UK motor industry rated fuses, versus other countries, back in the day. In modern (international market) cars you fit the Amps rating it says on the fuse box, which is the continuous Amps rating. That's because the actual fuses are marked with their continuous Amps rating. Whereas on old Lucas/BMC vehicles, the manufacturer also tells you the continuous Amps rating, but the fuses themselves are marked with their so-called "instant blow" rating. Apples and Oranges, from the days when people were expected to be more knowledgeable. (Before the days of "dumbing down".) Put simply, they've changed the standards.
Remember, the purpose of any fuse is to "protect the wiring". So you must fit a fuse that is capable of handling the continuous Amps, but will melt before the wires do -- the so-called instant blow rating. And that gives us a problem, because you can't simply replace a 35A glass fuse with its equivalent 35A blade fuse. As I've said, the glass 35A fuse is designed to carry only 17A continuously, whereas the blade fuse is designed to carry 35A continuously, and I've no idea at what Amps it will actually blow, other than that your wiring is likely to start smoking before the fuse blows.
Consequently, not only do I question why you'd swap out the manufacturer's perfectly good original equipment glass fuse box, but also why you're entertaining all this cost and work, instead of diagnosing what's called "the problem behind the problem"?
Finally, don't forget that fitting a different fuse box is what your insurance company calls a "modification". If your beloved Landy has the misfortune of going up in smoke, then your insurance assessor will probably go straight to your shiny new fuse box. S/he'll ask whether it was fitted (or certified) by a qualified auto electrician and, as you probably didn't notify the "modification" to your insurers, you're unlikely to get a pay out.
Disclaimer: this post is based upon my personal understanding, but I am not a qualified auto electrician, therefore, it is for discussion purposes only, and you are responsible for undertaking your own research by consulting a qualified auto electrician who is familiar with classic car fuses. No responsibility is accepted for errors or omissions. The purpose of this post is to raise your awareness of the difference between "continuous" and "instant blow" Amps in automotive fuses, so you can have a sensible conversation with your classic car fuse supplier.
Good-luck,
Rick
