All Truimphs - Electrical
A ConFUSEing Topic
by Randall Young - SCTOA Electrical Advisor
In a nutshell, NEVER put an American 35-amp fuse in your LBC! "Huh?? But my manual says 35-amps" you say? Let me explain. The problem is that Triumph used fuses that were rated according to a (now obsolete) British Standard. The current rating marked on the fuse was the current at which the fuse would blow immediately, rather than the American Standard (and now mostly worldwide) of marking fuses with the current they will carry. The result is that Lucas fuses are rated roughly twice what the same fuse would be rated in North America. So, that "35-amp" fuse that the book calls for is really a 17.5-amp fuse, and in fact some Lucas fuses do have this second rating printed on the paper inside the fuse. The big danger here is that with an American 35-amp fuse, if you have a short, the fuse may not blow. I've heard of at least one car being destroyed this way (the overheated wire caused a fire), so it's not just a nicety.
The correct Lucas fuses are also slightly smaller than the American Standard of 1-1/4" by 1/4", so it's best to use Lucas or replica fuses. They are available from most LBC vendors. However, it you're stuck on the road with a blown fuse, or like me, just too cheap to pay $0.75 for a fuse; common American fuses will work. They don't make 17.5-amp fuses, but the AGC 20 is an appropriate replacement for most Triumphs** an is availabe at any auto parts store, (** I've heard they will not fit into the fuse holder on a TR8).