TR2/3/3A TR3A fuses

[Tinkerman]

From what I see in the various shop books and catalogs there are only 3 fuses in the TR3. a 35 and 50 for the fuse box and a 25amp in-line fuse. Is this correct or am I missing something?

Thanks, Tinkerman

 

[martx-5]

There are only the two fuses in the fuse box as originally fitted. Any in line fuses would be the result of some accessory being added. Also, the amp ratings for the fuses (35 & 50) are the British amp rating. The amp rating for the fuses here are roughly HALF of the UK rating for an equivalent fuse.

 

[Tinkerman]

Thanks Art, I understand about the Brit rating and ours. In fact thanks to the BCF I am aware of the difference.

Tinkerman

 

[Geo Hahn]

Actually, later (US Spec) TR3As had a factory provided in-line fuse behind the dash panel. Even on cars not originally so equipped it is a good idea to add it as w/o it there is no protection for the rear light circuits.

 

[RedTR3]

OK, if adding the inline fuse, where in the circuit is a good place to add it?

 

[Geo Hahn]

The wiring diagram in the commonly available reprint of the owners manual (Practical Hints...) page 48 shows this fuse.

It is inline with the connection from the headlamp switch (S1) to the panel rheostat. That would be the connection to the panel switch on cars w/o a rheostat.

I believe on cars with the original-equipment inline fuse it may have clipped to the backside of the center panel along the lower edge. I just let mine sort of hang there as it isn't really going any place.

If you add the fuse to a car that did not originally have it you need to connect all the red wires to the panel light switch so the tailights and parking lights are protected (along with the panel lights).

If you look at both wiring diagrams (with fuse in owners manual and w/o fuse in Haynes) I think you will get the idea.

 

[Moseso]

Also, the amp ratings for the fuses (35 & 50) are the British amp rating. The amp rating for the fuses here are roughly HALF of the UK rating for an equivalent fuse.

OK... Tinkerman says he understands this, but I have never heard of such a thing before. Last I heard, the Ampere was a thoroughly international unit, unaffected by differences in metric or Imperial measurements. Can someone direct me to a proper explanation of "why LBC amps are different?"

 

[Andrew Mace]

It's not so much that there are "Imperial" vs. "US" amps. It's easier to understand, though, if you happen to have more modern replacement Lucas fuses. For example, the later Lucas "35 amp" fuses also tended to say on them "17 amps continuous"; in other words, the fuse can easily handle a normal constant load of 17 amps but would blow at anything beyond a very short surge of up to 35 amps.

Or something like that. I'm sure some EE can explain it better. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[Bugeye58]

It's a different rating system.
Here's an excerpt from an earlier post by Dave Russell. As with all of Dave's information, you can take it to the bank.
Thanks again, Dave.
Jeff

If you are wondering, you can replace Brit fuses with US fuses. Due to different rating systems, Brit fuses & US fuses will have different numbers for APPROXIMATELY the same ratings.

Brit (Lucas)--------US (SFE AGC)
5-----------------------3
10----------------------5
20---------------------10
25---------------------15
30---------------------15
35---------------------20
50---------------------25
Later Lucas fuses are dual marked to eliminate some of the confusion. An example is the 17/35. In this case the 17 is the approximate continuous current carrying capacity & 35 would be the fast blow rating.
This means that a single marked 35 or a dual marked 17/35 amp marked Lucas fuse is about the same as a 20 amp marked BUSS fuse.
D
Edit:
The US ratings are the continuous current carry ratings. In this case the Lucas fuse marked 35 or 17/35 would have a continuous rating of 17 & the US 20 rating would be close with it's continuous rating of 20.

 

[Moseso]

Got it... Thank you guys!