S4 Lighting relay where is it ???

[Luddite]

It would be interesting to see what the actual current draw on the blue wire is. After cutting the wire but before attaching the diode, you could put a multimeter set to amperes between the two ends and see what it reads with the indicators, pilot and tail lights on.

[Flip]

Originally Posted by LVC

It's on the 15A fuse marked as "Tail Light + Turns + Pilot Light" - 3rd up from the bottom on the box. The 7.5A one above it is for "Passing".

Your choice makes more sense to me, thx

I’m still not convinced the turn signal circuit should be on a lower current circuit than the headlight.

I checked on my YZF600R and the turn signals etc. including the fuel pump is on a 15amp fuse whereas the headlight is on a 20amp but the pattern is the same as my Monster.




Perhaps someone else with an S4 could have a look at their fuse box to confirm or deny my theory?

Originally Posted by Luddite

It would be interesting to see what the actual current draw on the blue wire is. After cutting the wire but before attaching the diode, you could put a multimeter set to amperes between the two ends and see what it reads with the indicators, pilot and tail lights on.

Yes I agree and I am sure it is pretty conservative but it wouldn’t be the first time Ducati have used rather marginal wiring on their motorcycles but either way I still don’t understand why a lower current rated diode would be used as if it’s having to work (which presumably it is) it’s only going to keep getting hot and eventually fail as this one did.

Excess heat on the rectification (diode) side is exactly why we get failures in the shunt type regulator/rectifiers.

[Luddite]

Originally Posted by Flip

Perhaps someone else with an S4 could have a look at their fuse box to confirm or deny my theory?

Now, we all know that Ducati owner's manuals can't always be taken as gospel but this is what the 2001 S4 one shows...





The blue wire goes into the fuse box at number 14 and the 6-14 fuse should be 15 amps.