I've started tracing and testing the electrical in my S3 rebuild. First dead fuse I came to fell apart when I got it out of the fuse panel. Pretty common for original Lucas fuses as I've read in many posts. They are also a slightly different length than U.S glass fuses by about 1/8". I haven't tried a U.S. fuse yet, but I've read that it's not a comfortable fit. Has anyone found a way to use modern blade fuses with some kind of adapter? I'm not interested in a complete fuse box conversion...….I'm just not. I see a slick little unit when I look at Google-Images, but they have either been discontinued (Jegs) or just are not available.

If anyone has a solution for this issue, I would appreciate any info. Thanks.
Dave

 

There are US fuse equivalents to the Lucas fuses. I wrote a post on my experience with the AC fans not working and copied a chart I found in that post.

 

I use BUSS fuses in my '84 without any issues as to the length of the fuse. Can't understand the problem.

 

Here's the amperage conversion
Fuse Conversion Chart

I've never had a problem using the Buss fuses either. They fit OK; the slight length mismatch doesn't matter

Cheers
DD

 

I didn't even know Lucas fuses existed as my car came to me with all BUSS fuses.
(';')

 

Thanks for your reply, here's what they look like Elinor.
Dave

 

I have replaced most of the original Lucas fuses but I saved them because they are so pretty.

 

My car has a mix of Lucas, buss and blade. No unusual issues. But, issues do exist.

Somewhere I have a chart of compatible Buss to Lucas.

The fact that original Lucas fuses still are present and function is a testimonial...

Sidebar: At times a mere roll of the fuse in the cradle restores function!! Been there, it work at times..

SidebarII: A visual inspection may not reveal an "open" fuse.

Carl

 

Thanks for the post, Carl. I do have the Buss-Lucas conversion info, but I'll replace bad fuses with local parts store parts (Buss). I am testing every circuit with DMM (volt/ohm meter); found a fuse that didn't get from here to there and when I pulled it out, the end caps just fell off the glass tube! I plan the replace all the fuses on general principle.

 

Bumping this as I am doing the same thing. I have the conversion chart but do the longer Bussmann AGC fuses fit?

Lucas Fuse is 1 1/8" long
Bussmann fuse is 1 1/4" long

Just from a visual it doesn't look like there is much extra room for the longer fuse. I know I can buy one and try, but there has to be a simple answer. I can get most of the original fuses from SNG Barrett, but some of them are on back order or special order only.

 

Google "Lucas Glass Fuse" and surely you can find whatever you need. Or David at Everyday XJ will send you some, I reckon.

The USA-style fuses come in various lengths, though. Here are some; I think there are others













Cheers
DD

 

AutoZone stores sell assortments of fuses for British & German cars:

https://www.autozone.com/electrical-...ece/32413_0_0?

 

After some searching, I THINK I found an assortment on Amazon that will work. The size was the first thing and finding fuses measuring 30mm long by 6mm around wasn't all that difficult, but finding a kit that included the higher amp fuses (50 amps or AGC 30 amps) was. Most kits seemed to only include up to AGC 20 amps. This kit seems to have everything from the lowest to the highest, when converted to AGC.

Please feel free to comment. Better to heed advice than burn the cat to the ground.

 

This is what I found that explains the differences. It seems there is a difference in the conversion amps from British to AGC depending on the site you land on.

From the August 2012 issue of Spokes, the Official Publication of the MG Car Club Western New York Centre.

Automotive Electrical Fuses -- British Vs American

British and American standards for rating electrical fuses are different. Both provide an “Amp Rating” for very similar looking fuses, but the two ratings mean very different things. The US system rates the fuse based on the continuous load it can handle for a specified period of time w/o blowing, whilst the British system expresses the load at which the fuse will immediately blow.

That’s a significant difference! As an example, the 35 Amp fuse called out for many 1950’s/ 60’s/ 70’s vintage British cars (Lotus Elan & Europa for sure) is roughly equivalent to a US-spec BUSS AGC 17 Amp fuse. Install a US 35 Amp fuse into your fuse box and the wiring harness will melt down before the fuse blows.

DO NOT use a USA rated 35 amp fuse in your vintage British car!

The complete rating for the 35 amp Lucas fuse is - “17 AMPS CONTINUOUS / 35 AMP SURGE”

Early British fuses were simply marked with the quick-blow rating, but later fuses are given two ratings in an effort to minimize the confusion. For instance, the 35 Amp fuse is often marked as “17 continuous / 35 blow”, or simply 17/35. In that case, use the lower “continuous” rating as the one to which you try to match an American BUSS fuse rating. Or, better yet, proper British fuses are available from your favorite independent British car parts dealer.

The comparison/ substitution looks something like this..

British Lucas Fuse vs American BUSS Fuse
Fast Blow Dual Rating to AGC
50 amp or 25/50 amp is equal to 25 amp AGC
35 amp or 17/35 amp is equal to 17 amp AGC
30 amp or 15/30 amp is equal to 15 amp AGC
25 amp or 12/25 amp is equal to 12 amp AGC
20 amp or 10/20 amp is equal to 10 amp AGC
15 amp or 7.5/15 amp is equal to 8 amp AGC
10 amp or 7/10 amp is equal to 5 amp AGC
5 amp or 2.5/5 amp is equal to 3 amp AGC
2 amp or 1/2 amp is equal to 1 amp AGC

Unfortunately, there’s no extra data marked on either the fuse body or on the package to tip-off the user that the ratings are different. It’s very important that USA owners of British cars be aware of the issue and make wise choices when using USA fuses in them. The best choice is to make the effort to source proper British fuses. In an emergency, the loose Rule of Thumb is to use a USA BUSS fuse with an Amp rating equal to no more than one half of the British Lucas fuse rating.

USA BUSS fuse terms:

SFE fuses are "automotive" and rated to interrupt only 32 volts. Their length depends on their current rating, ranging from 5/8" for a SFE-4, to 1-7/16" for a SFE-30 (lower amperage = shorter and higher amperage = longer). So, size-wise, sometimes higher amp rating SFE fuse will work in place of an "AGC" or an "AGA" or a Lucas fuse. Regardless of physical size, an SFE will always blow more quickly than a current AG (or older AG) that has a similar Amp rating.

AGC fuses are “General Purpose”. They are always 1/4" Dia X 1-1/4" long. They’re available in 250V ratings to 10 amps, and up to 32V ratings to 30 amps. AGC fuses are approximately the same length as British fuses and will fit in the Lucas fuse holder. An AGC-20 is the same length as an SFE-20 and they are pretty much interchangeable.

Both AGC and SFE are "fast acting", but according to BUSS charts, the SFE is faster. An AGC-20 is rated to carry 27 amps for up to 60 minutes, while an SFE-20 will blow in under 2 minutes. However, the 60 minutes is given as a maximum, while the 2 minutes is apparently typical, so that may not be an accurate comparison. Without getting too lost in the details, the basic idea is that an SFE will blow faster than an AGC and will better protect your LBC’s vintage wiring.

If you are going to use BUSS fuses, then when availability and length permits, use SFE fuses as your first choice. When you must use AGC fuses, shop for the 32 volt rated versions first, but the 250-volt AGC fuses will “work”. SFE fuses in lower Amp ratings will be shorter than the Lucas fuses and may not fit the Lucas fuse box properly.

Currently BUSS AG fuses are available in different lengths, denoted as AGA, AGB and AGC. They are all available in the same voltage and current ratings, the difference being in the lengths. AGA is the shortest, and lengths become longer as they progress from A through C.

Previously, the AG fuses were differentiated on a number scale, 1AG, 2AG and 3AG. The older "3AG" fuses are the same as the modern, common "AGC" fuses. Similarly: 1AG = AGA and 2AG = AGB. I don't believe stores or catalogs list "3AG" or "1AG" fuses anymore; they just list the current designation "AGC" or "AGA" now.