S1 Fuses Help Please

[My S1]

I'm rebuilding my S1 fuse box and finding a smorgasbord of fuses.  Neither the wiring diagram in my manual and the beautiful color wiring diagram that Ray Bisordi made, do not specifically call out fuse sizes.  The manual makes no specific reference to them (2) other than to say that the spares should be 35 Amp.  Am I to assume that that means both/all are 35 Amp?  Just want to make sure.   

[TurboFource]

I learned on here that 35 British Amps is not the same as here …. I think it is like 17 Amps ….

[bjthomp]

Each of the two active fuses are 35 amp, as are the two inactive fuses that are supplied as spares. I don't know anything about comparable British/American fuse ratings, but I do use nothing but fuses that I have purchased from a British parts vendor, typically RD.   

[314159td]

Do not attempt to match the original sizes - there are various types of fuse ratings which have changed over time. Determine the typical load using a DC current clamp meter, and choose a fuse the next size up from that value.
Also consult a chart like this, to ensure your fuse is not oversized for the wire it protects. That is how car fires happen.

This entire article is pretty good at explaining wire sizing, which is still relevant in determining fuse sizes.

My favorite (lazy) way - buy a whole pack of glass fuses and step up the sizes until they stop blowing on a regular basis. Turn on everything all at once and see what happens, have identified a few dangerous circuits in conjunction with a thermal camera.

[dakazman]

 I think this might help  pg 20
http://www.lotus-europa.com/manuals/misc/electrical/BritWiringCatalog.pdf
 Dakazman

[EuropaTC]

That fuse box is like the ones used on the Elan, my '68 Elan came with exactly the same box and 35amp fuses.  Although the fuses come with 35 amps on them I think that meant it was rated for 17.5amp continuous with 35 amp fuse blow.  IIRC it's the same as was used on the original BMC Mini and no doubt loads of cheaper British cars.

Unless you want to restore for concours as it left the factory, I'd strongly suggest you fit a fuse box with more circuits/fuses if only because it will make fault finding easier. I never had a problem with the Elan but even so it's got a 4 fuse system now. The later Europa spec is better but even so, more fuses just make life easier. 

Although I never had a problem with the 2x35amp fuses on the Elan there's a thread running here on the current draw from the window motors and there's mention of 15amps running, 20amps max at stop. That sounds awfully close to the 17.5amp continuous rating, especially if you have wipers/headlights on as well ?

https://www.lotuseuropa.org/LotusForum/index.php?topic=6907.15   

[My S1]

Thank you all for your input.  It was a bit of a dumb question, but it was certainly dumb luck for the previous owners to be driving around with a 5 amp fuse on a 35 amp load ignition feed circuit.  I'll retain the original, old Elan box but keep my nose alert for smoking wires.

[jbcollier]

It is absolutely not a dumb question.  Cars have gone up in smoke when fitted with the wrong 35A fuse.

Please replace the original fuse box.  There are riveted connections that corrode over the decades and can cause mysterious issues.  There are new ones available.

[My S1]

R.D. Ent has a box that looks very similar to the original.  Guess I'll give them some more cash...