 | Home > Maintenance & Modifications > Lightforce 170s - what fuses to uses? |
 
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610   
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Current(Amps) = Power (wattage) divided by voltage.
Yes of course you need to change the fuse! Each 100 watt filament will draw approximately 8.5 amps in comparison to just under 5 amps each for your 55 watt ones. If you go through life with your head in the sand....all people will see is an ar5e!! Treat every day as if it is your last....one day you will be right!! |
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9th Oct 2013 11:59am |
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| BigWheels Member Since: 21 Mar 2010 Location: Somerset Posts: 1405 
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So you recommend a 20? Land Rover Defenders. 67 years heritage, minimal appearance changes, still going strong all over the world. Not a fashion vehicle, but fashionable to own. Made for the needy, not the greedy. Ta ta Defender
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9th Oct 2013 12:03pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20489
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20A for two 100w lights. K9 is bang on the money.
Roos on mine at the same wattage and the fuse needs to be close to the battery too. No Guts, No Glory. 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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9th Oct 2013 12:15pm |
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| SteveG Member Since: 29 Nov 2011 Location: Norfolk Posts: 661 
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If wiring independently 10A is ok. If in one circuit it depends on no. of lamps
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9th Oct 2013 12:17pm |
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| BigWheels Member Since: 21 Mar 2010 Location: Somerset Posts: 1405
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Currently I have a separate fuse under the bonnet, so presume that would be it. It was fitted along with the auxilary lights. Land Rover Defenders. 67 years heritage, minimal appearance changes, still going strong all over the world. Not a fashion vehicle, but fashionable to own. Made for the needy, not the greedy. Ta ta Defender
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9th Oct 2013 12:48pm |
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| SteveG Member Since: 29 Nov 2011 Location: Norfolk Posts: 661
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???? You'll have to explain that one to me  |
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9th Oct 2013 1:12pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20489
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Fuse needs to be close to the battery to protect the whole cable, fitting a fuse half way worse close to the item means the cable is not fully protected. The fuse is there to protect the cable not the item you intend to use.
For example any short in the cable (positive run) with the fuse near the battery the fuse will blow which will break the circuit and stop a possible fire. If you have that fuse half way along that wire or nearer the item I.e. The lights the fuse will only protect the cable nearer the lights and the whole rest of it is not protected at all so if it shorts between the battery and fuse there's nothing to stop it. Cable will go red rod burn off the insulation in a very fast timed melt anything in its patch and probably catch fire. K9 please correct me if wrong.... No Guts, No Glory. 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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9th Oct 2013 1:53pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1430 
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^^^^ +1 That was what I was taught. It is not always phsically practical, but is best practice
 Just look at house wiring, perfect example  |
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9th Oct 2013 2:11pm |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610
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Customsteve is correct in principle it is always 'best practice' to ensure fuses are placed as close as possible to the power source. Nevertheless in the case of vehicle electrical power distribution the secondary fuses are normally protected themselves by a higher rated fuse protecting several different circuits or a mega fuse off the battery terminal itself.
If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! |
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9th Oct 2013 2:14pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20489
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I was thinking that but it will still be much much higher rated than the wiring is. No Guts, No Glory.
🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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9th Oct 2013 2:28pm |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610
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Maybe so but the time it takes for a fuse to reach rupturing current with a direct short will be much quicker than the wire heating up and self combusting. In extreme cases the wire will vaporise or open circuit before ignition.
Quick look at the diagrams reveal relay coils for lighting protected by 5 amp fuse, headlamps by a 10 amp, subsequently protected by a larger 30 amp. The 30 amp would blow irrespective whether the 5 & 10 were in the circuit in a direct short scenario. If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! Last edited by K9F on 9th Oct 2013 5:41pm. Edited 1 time in total |
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9th Oct 2013 5:35pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20489
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 No Guts, No Glory.
🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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9th Oct 2013 5:40pm |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610
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^^^^
With inadequate circuit protection of course. The wire/cable then in effect become the fuse. If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! |
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9th Oct 2013 5:43pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20489
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I have seen a wire glowing red hot on a shorting wire on an old mini, not something I would have ever wanted to own. You'd only have to touch the thing and the wiring would short all over the place. No Guts, No Glory.
🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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9th Oct 2013 5:54pm |
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