rev counter and horn not working.

[Kes]

Hi people. The rev counter and horn have stopped working on my '69 S2 roadster. I guess they must share the same fuse or earthing point? anyone have any ideas how I might fix it? Cheers.

[Michaelg]

Almost certainly the fuse as same happened to me. First I knew was the fan ceasing to work and the engine overheating as that was on the same circuit on my S2. The fuse needed uprating.

[Keith in Norfolk]

Yep have had same problem , mine turned out to be the fuse holder itself not the fuse ( change both )

[malcolm]

Kes, is this the same horn you're working on from 4 years ago?

[Hugo]

Yep have had same problem , mine turned out to be the fuse holder itself not the fuse ( change both )

If the fuse holder has melted, it suggests there is an overload somewhere. It is surprising how often you can overload a circuit and melt plastic components without blowing a fuse, even if it's the correct rating. If you get a short, the fuse will blow, but if it's a gradual overload, things can get hot without the fuse blowing. I nearly had a house burn down like that in Florida. Melted the wires together but never tripped the circuit breaker.

[Series1 Stu]

Plastic melting in this way is more likely to be caused by tracking to earth, rather than an overload. Check it's all clean around the fuse holders and make sure the wire crimps are all tight too. Clearly something is causing enough heat to slowly melt the fuse holder plastics.

It's usually a degenerative thing, rather than an instantaneous event.

Regards

[mgcjag]

Kes as Malcom said above....you had the same fault 4 years ago.... viewtopic.php?f=5&t=4780&p=87477&hilit= ... ter#p87477

[Spinner]

The Horn relay, Tacho and several other items are controlled from fuse 6. It is rated at 35amps. Replace the fuse with 35amps do not uprate it. If you have the failure again, you need to trace the cause.

[Hugo]

There is a difference, is there not, between British and American fuse ratings. A British 35 amp fuse is actually rated at 17.5 amps if I remember rightly, whereas an American 35 fuse is rated at - wait for it - 35 amps. The logic behind the British rating is that a 17.5 amp fuse will blow at double its capacity.

[mgcjag]

Once again re fuse rating.......the fuse ratings on the plate are given in blow rating i.e. the maximum current carried before the fuse blows. Modern fuses give the continuous rating which is usually about half the blow rating. So a 17A fuse (= 35A blow rating).....etc

[Spinner]

There is a difference, is there not, between British and American fuse ratings. A British 35 amp fuse is actually rated at 17.5 amps if I remember rightly, whereas an American 35 fuse is rated at - wait for it - 35 amps. The logic behind the British rating is that a 17.5 amp fuse will blow at double its capacity.

I have a full explanation of this but cannot paste it into this forum.