OEM Lucas Fusebox and glass fuse size

[Marsu]

I bought some glass fuses from the local auto parts store and found that they don't fit into fuse box, being at least 3mm too long, at 31mm overall.

I've called a few alternative suppliers and no-one seems to keep anything at the right length.

Has anyone else encountered this problem?

[Odd]

Yes, lot's of us have in times gone by...
So I've collected some data over the years that might be of interest to other Wedgies
who haven't noticed this before:

-----Saved Messages-----
> ... close to the correct rating? Installing a fuse with too high a rating could be inviting melted
> wires and a possible fire. You don't want that.


OK friends,
Wayne's mail made me think - so I went out to my TR8 and took out my little stash of old original
Lucas fuses [from the era when they were labelled with both of their current ratings]:

A Lucas fuse is rated by what current it would blow at.
Ordinary automotive fuses are rated by what current you can draw WITHOUT blowing them, or
the maximum continuous current. They don't really specify at what current they'll blow...

Anyway, these old Lucas fuses of mine have both the Lucas "will blow at" rating, and the maximum
continuous current rating, i.e. the normal rating labelled on them. [Or rather in them, because it is
a small paper strip inside that carries this info. The more modern Lucas fuses have the info printed
on the glass tube in an abbreviated form.]

So here's your equivalents:

Lucas 50 amp - continuous 25 amp - part number GFS3050
Lucas 35 amp - continuous 17 amp - part number GFS3035
Lucas 25 amp - continuous 12 amp - part number GFS3025
Lucas 20 amp - continuous 10 amp - part number GFS3020
Lucas 15 amp - continuous 8 amp - part number GFS3015
Lucas 10 amp - continuous 5 amp - part number GFS3010
Lucas 8 amp - continuous 4 amp - part number GFS3008 - NLA
Lucas 5 amp - continuous 3 amp - part number GFS3005
Lucas 3 amp - continuous 1.5amp - part number GFS3003
Lucas 2 amp - continuous 1 amp - part number GFS3002 - NLA

See the trend here?
Each fuse is actually good for a continuous current that's roughly 50% of it's Lucas rating.

BUT!
Another, and just as important, issue to take into account is the fact that the Lucas fuses
have a different physical size as compared to the standard item. [Who would be surprised!?]

The Lucas 1/4" diameter glass tube fuse is 1 and 5/32" [~29.4mm] long, (max tolerance + sloppy manuf.)
while the standard 1/4" glass tube fuse is 1 and 1/4" [~32.0mm] long. (max tolerance + sloppy manuf.)

This makes it more than a tight squeeze - loading the fuse holder plastic with undesired stress
if you force a standard fuse into the Wedge fuse block... So typically British...

Best regards
/Odd

PS
I order my Lucas fuses from Rimmers when I have something else on order from them
- So by now I have a nice selection in my garage, they are never a problem any more...

----- Another saved message -----
C F wrote:
> As I persist in describing it wrong could someone out there PLEASE clarify the difference
> between British fuses and American fuses with regard to ratings.


T B answered:
A British Standard automotive fuse will run continuously at 1/2 its rating but will blow quickly at its
rating. For example, a "35A" fuse will never blow at 17A but will melt quickly at 35A - you may see
"17A continous 35A blow" printed on the paper inside the fuse or on the glass envelope.
These fuses meet the IEC publication 127 standard for time/current curves, and have a fuse
element that appears to be a thin round wire of uniform diameter through its length.

An ordinary automotive fuse will run continuously at 110% of its rating and will blow within 4
minutes at twice its rating. The fuse element is a flat piece of metal and may have a narrowed
center section. The fuse rating is stamped in the metal end cap(s).
(Underwriter's Laboratories spec 248-14 states that the fuse must carry 110% of its ampere rating
and must stabilize at a temperature that does not exceed a 75C rise at 100%. The fuse must
open at 135% of rated current within one hour. It also must open at 200% of rated current within
2 minutes for 0-30 ampere ratings and 4 minutes for 35-60 ampere ratings.)
Using the same "35A" fuse in the IEC example, it would never blow at 38.5 amps, will blow in
two hours at 47.25 amps, and within four minutes at 70 amps.

We will have a tech session concerning this topic at the 2005 VTR National Convention.
This demonstration will be done outside so we don't set off the smoke detectors in the
convention center when we melt the wiring harness before blowing the fuse...

Here's a picture comparison of the two glass fuse types:


----- End -----


<font color="red"><b>My two 1980 Wedges...</b></font id="red">

[dursleyman]

I know this is an old thread but thought this picture would confirm the text. Took it out of a fuse I blew this week.



Russ

1980 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

[Sautie]

Another caveat. Some years ago the indicators on my 8 refused to work but the hazard lights worked perfectly & of course they run off the same fuse. Much head scratching & debate. Fortunately I know an auto electrical shop owned by an ex Lucas apprentice. He took out the fuse and called it a piece of shit. He then broke the glass & one end cap fell off the fuse wire.
He explained that it was either a Japanese or Chinese fuse who both used a "cold solder" inside the end caps to fix the actual fuse wire & these came loose causing a " cold" connection. Thus on indicators with 2 bulbs flashing the current was too small to jump the gap but on hazards the current flowing with 4 bulbs would jump the gap. He advised me to only use English fuses that are identifiable by the fact that the fuse wire goes through the end caps and is attached by a blob of solder that is on the outside of the end cap. The "shit" fuses have smooth tops to the end caps.[8D]

[FI Spyder]

I never check these glass fuses visually but with an ohm meter because the wire may be "broken" outside of the visible part. The metal end caps can come loose with age contributing to the problem.

- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT