TR2/3/3A The under dash fuse on later TR3's

[karls59tr]

If this fuse blows does it knock out everything else? What size should it be?

 

[6TTR3A]

You lose the secondary lighting system. ( Tail lights, turn signals, license light and dash panel lights)
It was mandated on US export cars only made around TS50000 onward. A 15 amp fuse will suffice.
Frank

 

[Geo Hahn]

Not a big fuse - I think the original was a 35amp using the British system - so no more than a 20 amp if you're buying a Buss fuse at the FLAPS. In fact you may find something like a 14amp American fuse is a closer physical size and would be adequate.

 

[sp53]

I thought it was just for the tail lights, but not sure. My experience was that the fuse was kind of hit and miss; some cars had it and others did not. I can say the tails lights needed something because if they shorted out that wirer would melt the harness right to the switch and cause a major ugly plus let a lot of smoke out.

 

[Geo Hahn]

I thought it was just for the tail lights, but not sure...

Dash lights, tail lamps, side lamps -- here is a typical (late-TR3A) diagram. The fuse is item 41:

 

[martx-5]

I find those original diagrams not so easy to follow. It's nice that they put everything in it's relative position in the car, but that turns it into a maze of wires. I find the diagrams from Advance Auto Wire are pretty much foolproof to follow. On the TR3A-TR3B diagram below, you'll see the fuse coming off the lighting switch and all that it drives, in one neat place.

https://www.advanceautowire.com/tr24a.pdf

 

[TR3driver]

I just want to point out that, contrary to many sources, that fuse does not affect turn signals or brake lights.
Just dash, tail and parking lights.

Piggott stated a fuse was added for brake lights, but he was mistaken.

A correct description can be found in Practical Hints, along with the (Lucas) rating of 25 amps. An AGC 10 seems to work fine for me, even before I started converting to LED.

PS TS39781LO had that fuse originally. I added one to TS13571L, but it didn't have it originally.

 

[Brinkerhoff]

and ( if I might add) , the license plate lamp which is in the same red wire circuit . That lamp is pretty vulnerable to being crushed in a minor impact which could easily cause a short that would burn the entire circuit !