If one shifts from glass cylinder fuses to blade uses I recall there is a different system of rating for these so the old glass fuses for 7.5, 10 and 15 become what?
It's to do with quick or slow to blow from memory or maybe it was more complex than that...

 

I remember a chart or something from my Lucas days, and its gone, bugga.

I found this, it might assist.

The Lucas bit at the bottom goes into the flow, instant, fused detail, and I read it 3 times before it sank in, bloody confusing all the same.

https://en.wikipedia.org/wiki/Fuse_(automotive)

 

So this chart of Wiki. The two left columns related to new fuses and the two right ones to Lucas glass type fuses in their instant and continuous forms?
Or not?

 

OK, my reading, and this is from 50 odd years ago when at Lucas.

The Continuous Amps is the rating on that circuit, where the fuse normally operates. That fuse will "blow" at the Continuous Fusing Amps.
The Instantaneous is what it says, POP, as soon as the circuit is alive, thus a short circuit.

On that chart above, the 1st lkine:
Is a 3AMP circuit,
Blows at 3.5Amp
The rated fuse is a 1.5Amp IN LUCAS TALK.
Bloody confusing.

When I did the NEW Glass fuses in all the S2 and XJS beasts, I basically read the fuse, a 10amp, got a 15 as a replacement, a 15 got a 20, and so on.

NONE of those cars had issues, and NONE of those cars melted anything, or caught fire due to my fuse selection.

There would be something, I feel sure, on Google, but I have not found it in a quickie search.

 

No, Aden . . . the answer is a definite NOT . . .

All columns in this chart relate to the conical ended ceramic fuses, not glass fuses, and no differentiation is made in these for 'slo-blow' or 'fast-blo' which, while they serve some esoteric purposes in areas like output stages of amplifiers, have no widespread auto application.

Moreover, the chart gives only the performance ratings for those ceramic fuses and implies no transferability to or from either glass or modern blade fuses. I take it you understand the difference between columns 2,3,4 but see no relevance if you are changing from glass fuses to blade.

That said, and as indicated in the columns, they are rated to pass a certain current continuously (ie even after the cows come home); or fuse at some indeterminant time at a higher current; but fuse instantly at some even higher current.

I would suggest you Google for similar performance charts for the two types of fuses you are interested in or . . . do as I would do, by sacrificing a couple of 10Amp fuses under controlled load conditions from 10A to 20A and noted the expiry of each. My bet is that they will pass their marked rating (10A) but fail at a similar higher current.

Best wishes Aden, and please let us know your results.

Ken

 

Hmmm . . .

In light of Grant's reply, with which you can compare my similar approach, maybe I have misunderstood your intention, but I still don;t see the relevance of a chart on the Lucas ceramic fuses to your task which I believe is to replace common glass with modern blade.

Ken

 

I don't know if this is what you are referring to or not, but I came across a chart when replacing blown glass fuses. I didn't know this before. It turns out that the glass fuses by Lucas are rated at the "Blown" amps rather than "Continuous" amps. American BUSS glass fuses are rated in continuous amps. So if you put an american 50A glass fuse in for a Lucas 50A fuse you are seriously overdoing it. The American Fuses are like half the rating. There is a chart and I even copied it out in one of my threads. Doug has also put this chart up. I would imagine new blade fuses might be set up and rated the same way as the American glass fuses with continuous amps.

 

YUP. Values remain Buss blade or glass.

 

Hi everyone,
The simplest way I've found to explain the difference on fuse ratings after research is as follows:

The Lucas rating is the INSTANT blow current, the American ( AGC glass fuses etc) rating is the continuous carry current ( it will take a good bit more to make it blow, so your wiring might melt or catch fire first ! ).

The original British / Lucas glass fuses are the only ones ( that I know of ) that are rated differently, American glass fuses are rated the same as newer blade types etc = continuous current

Below is a conversion chart I found online. I have a printed copy in all my cars / manuals just in case. Only the 20A SFE will also fit because SFE fuse's length varies by rating ( AGC's are 1 1/4" long regardless of rating ).

Hope this helps !
Brian

Lucas AGC
Instant Constant
2 1
5 3
10 5
15 8
20 10
25 12
30 15
35 17 ( or 20 SFE, right length slightly faster blow )
50 25

 

Grrrrr !
My extra spaces between columns keep getting deleted back to only one space ! Hopefully everyone can figure it out, guess I'll have to up a picture instead !



Cheers !
Brian

 

I did another Google, too cold and wet to visit the Jags.

I found this on our OWN Forums, and is I THINK, what is being asked for.

https://www.jaguarforums.com/forum/x...rating-179922/

If I am WRONG, I will stay in the naughty corner with Jack until it settles.

My fuse changes on MY cars for post purchase reasons, was purely what I wanted. The stupid 50amp in the block for the A/C etc was REMOVED, the circuits split, and 2 thermal circuit breakers used under the dash. PITA and glad I did it when I was 30+ years younger, as today, NO chance.

 

these make sense
10 5
15 8
20 10

but i also have a number of 7.5 ? what side of caution do I go on here

 

this is a good ref to have for future

The original British / Lucas glass fuses are the only ones ( that I know of ) that are rated differently, American glass fuses are rated the same as newer blade types etc = continuous current

 

Hi,
I'm not sure about a Series 2, since I only have 3's that don't have any 7.5A fuses. Is that what the fuse cover label / owners manual shows or is that what you found installed ? If it's a plain glass fuse instead of a Lucas with the paper label inside, it might be an "American" 7.5A "continuous" which could be used for Lucas 15A "instant".


Cheers,
Brian

 

seems to be what the backing paper says but it might not be an original perhaps.

actually on examination...

removing and flipping it over, different story. seems to have a what .. a range i.e. 8 10 7 etc

these much to the Lucas ratings.

side B must be US ratings?

original printed side A Lucas ratings?

 

correction, the side numbers are sequential and must ref to the terminal/connection/wiring number or such on a wiring diagram I guess.

 

Hi,
I believe you are right on all counts, A side is "Lucas" instant blow amps & term numbers, B side is constant carry amps.
Here is a link posted in another thread that has a chart with slightly different conversion values. I think either version should be safe to use but I take no financial, legal, or emotional responsibility !

Fuse Conversion Chart

Cheers,
Brian

 

What? Emotional?
I thought I was the only one who cried in the presence of Jaguars???

Cheers,

 

HAHAHAHA Ken,tears of Gold.

What happened to the days of a piece of Silver Foil, AKA Chocolate Bar Wrapper, twisted around the blown fuse, and onward ho the Jag.

OR

Fencing wire, farmers supplied us plenty of that when needed.

 

HAHAHA . . . Grant Francis . . . Son Of McGyver ???
Cheers mate,
Ken