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Re: best solutions for dash panel wiring connections?

Ian with a total of (18x2) + (6x2) Watts you will have a draw of 48w, divide by your voltage of 6v equals 8amps. So a fuse of 12amps would be safe. I don't know the ampere rating of the horn but would fuse the it separately as the current may be beyond this rating, I would expect that a 30 amp will provide safety. This site may give you some insight into the requirements, http://www.12voltplanet.co.uk/fuses-guide-uses.htm
(I personally don't like the inline type of fuse holder as they are subject to being tugged and movement causing bad contacts which can cause them to get hot and melt (had this happen years ago on a 105E Anglia, nasty smell from under dash). Use a more modern fusebox.

Location: Piddle Valley

Re: best solutions for dash panel wiring connections?

Thanks Peter for working out the correct fuse for me. I thought there used to be an issue with those holders, but forgot what it was. David Cs choice looks good, will need to see if they do a 12amp fuse in the small one. I also have a bulb horn, so could use that at night if I go with the 12 amp fuse.
Cheers Ian

Re: best solutions for dash panel wiring connections?

Ian Moorcraft
David C's choice looks good, will need to see if they do a 12amp fuse in the small one. I also have a bulb horn, so could use that at night if I go with the 12 amp fuse.

Continental fuses are available in 5A, 8A, 16A & 25A. Values on fuses are the continuous ratings - will blow at double this figure.

Re: best solutions for dash panel wiring connections?

David Cochrane
Ian Moorcraft
David C's choice looks good, will need to see if they do a 12amp fuse in the small one. I also have a bulb horn, so could use that at night if I go with the 12 amp fuse.

Continental fuses are available in 5A, 8A, 16A & 25A. Values on fuses are the continuous ratings - will blow at double this figure.


Thanks David, I have to admit being a bit thick on this subject, to get the protection value of Peters 12 amp suggestion do I need to go up or down with the fuse choice if it blows at double the figure?

Re: best solutions for dash panel wiring connections?

Sorry Ian I should have said that the continuous rating of 8amps requires a 12amp blow rated fuse. Given that 12 is not available get the closest you can.I'd probably go to the next one up to cover any additional items that you may fit later.
Fuse ratings

Continuous rating
Fuse are marked with the current that they will continuously pass (at a standard temperature) without blowing, known as the continuous rating. It is good practice not to allow the continuous current to exceed 75% of the fuse's rated value to accommodate momentary current surges that might cause the fuse to fatigue over time or blow unnecessarily (nuisance blow).

Blow rating
In simplified terms this is the current rating at which the fuse will blow. Most fuses have a blow rating around twice that of the marked continuous rating. So a 5A continuously rated fuse will have a blow rating of 10A.

Some older style fuses may still be marked with the blow rating rather than the continuous rating so care should be taken when replacing an older style fuse with a modern one that the ratings are understood and the correct fuse used.

Location: Piddle Valley

Re: best solutions for dash panel wiring connections?

Many thanks again Peter for your comprehensive explanation, so it looks like a 16amp will be my choice.
I have never given much thought to the simple fuse and I am sure many others likewise, it's likely others on the forum have also gained knowledge from your reply. Ian M

Re: best solutions for dash panel wiring connections?

so to summarise.... please correct me if wrong....in essence, putting a 16A fuse in the line to the ammeter would give safety for all systems, rather than putting something in specifically for the headlights downstream of the switch?

and if there is an original fuse box (i.e. 1934 onwards, there is the single fuse box for horn trafficator and something else) elsewhere, that's not a problem, just another layer of protection?

Re: best solutions for dash panel wiring connections?

Last bit of help appreciated on this one the fuses I have bought to protect horn/ 18w headlights/ 6w tail lights all together, are marked F15AL 250VLAC does this fit with the load/blow values suggested above. IanM

Re: best solutions for dash panel wiring connections?

Just bringing this to the top again hoping for an answer.



Ian Moorcraft
Last bit of help appreciated on this one the fuses I have bought to protect horn/ 18w headlights/ 6w tail lights all together, are marked F15AL 250VLAC does this fit with the load/blow values suggested above. IanM

Re: best solutions for dash panel wiring connections?

Ian , what horn do you have fitted?

Location: Piddle Valley

Re: best solutions for dash panel wiring connections?

Hi Peter standard original Rist.

Re: best solutions for dash panel wiring connections?

Ian , I'm not sure what the current draw of the Rist is but the fuse you have should be ok for the light circuit. I would probably wire the horn independently, you could wire it direct from the battery, or spur from the INPUT side of the ammeter. The lucas type "electro-magnet " type of horn do pull a fair bit of current and are usually wired via a fused relay.
 photo horn image001.jpg

Location: Piddle Valley

Re: best solutions for dash panel wiring connections?

Many thanks again for your help Peter, it is much appreciated. IanM

Re: best solutions for dash panel wiring connections?

Hi Peter,
whilst you can wire up the horn as you show, for cars with a horn push in the center of the steering wheel, that is not how they are / were wired originally.

The correct wiring is to have a permanent live feed to one side of the horn, (IE not the earth) and the horn push connects to the other terminal on the earth side - that way if the cable in the steering column wears you only get an irritating random sounding of the horn and not a direct shorting to earth of the live feed which would likely burn out the wiring.

Steve V.

Location: Polegate, East Sussex, United Kingdom

Re: best solutions for dash panel wiring connections?

Sorry for the error , you're quite right, the push switch should be on the earth side of the horn.

Location: Piddle Valley