I have a std sierra set up and, now again (every 3 months or so), the fuse goes.
Normally evening just around dusk as I am going on the m'way - which I am sure is coincidence. It does make for a rather interesting drive though!
I change the fuse and all is fine.. until it goes again.
I tried replacing the relay and it did not make any difference so went back to the original.
In general the connections at the bulbs look OK with no sign of anything too hot.
The fuse is 10A. I have not checked what else is on this circuit. Can you get LED replacement bulbs that would work with the std Ford relay as this would get round the problem (I have replaced the other bulbs with LEDs except the headlights?
Any suggestions?
Alex

What happens if you use the hazards?

You have a short circuit somewhere I would guess but thats the trouble with intermittent electrical faults very hard to trace unless you check over the loom.

I think the hazards went as well but will confirm tonight buy putting the old fuse back in.
Could arching in the indicator switch cause the fuse to go? ie can sparking or arching draw more current?

I wouldn't have thought enough to blow a 10amp fuse but those with far more knowledge than me should be able to give you more of an idea.

what value fuse are you using?

for a standard configuration of 2x21W + 5+ 2 ~ 50W
which at nominally 12v is 4A
though a 5A fuse should work 10A might be more suitable

According to the wiring diagram, I have indicators, reverse and stop lights on the same circuit and it has a 10A fuse as I say above.

If your switches have ever got wet they can corrode internally and short out , try giving them a squirt of contact cleaner or even WD40 Pretty sure if you do a search it has been covered several times, I know at least one Viento owner who had major problems