 | Home > In Car Electronics > Durite 4 way fuse board passes some current with no fuses |
 
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| rallysteve Member Since: 10 Feb 2014 Location: Cumbria Posts: 2199   
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Yeah that sounds right. I think the LEDs should go out once you put a fuse in.
Steve 02' 110 TD5 Double Cab Rebuild Thread 84' 90 3.9 V8 Caged Pickup Build Thread - Now For Sale Mobile Diesel Heater Build Thread |
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13th Feb 2017 10:18pm |
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| Fifth Horseman Member Since: 08 Mar 2011 Location: Lanarkshire Posts: 322 
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Indeed a small amount of current is needed to illuminate the LED, typically in the order of 20mA (0.02A) for a LED similar to that on the fuse box. A LED work lamp will require upwards of 0.2A (high power ones can draw a lot more).
The LED in series with a current limiting resistor is connected across the fuse terminals so that if/when the fuse blows enough current can flow through the LED to illuminate it but not enough current to cause any damage, so it is not strictly accurate to say the circuit is operating unfused. To summarise, the board is operating as intended. Last edited by Fifth Horseman on 13th Feb 2017 10:23pm. Edited 1 time in total |
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13th Feb 2017 10:21pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16876 
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Totally to be expected with that type of box with the daft leds.
The leds are in parallel with the fuses and are normally shorted out by the fuse. In the event of a short circuit to ground on the load side of the fusebox, the high current will blow the fuse and the earth path through the short will ground the cathode of the led and, since the anode is still connected to the (unfused side of the) positive supply, the led lights. Personally I detest the things, they're unnecessary, and I want a fuse to isolate the fault completely when it blows. |
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13th Feb 2017 10:22pm |
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| Fifth Horseman Member Since: 08 Mar 2011 Location: Lanarkshire Posts: 322
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I agree that although there are applications where "fuse fail" indicators can be useful, the automotive sector is generally not one of them.
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13th Feb 2017 10:29pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 19572
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If they are a must, of which I wouldn't use them you can get actual fuses that do the same thing.
You can then pull the fuse in question, if needed. I'm not a fan either. Diesel$ Live$ Matter. ⛽️🛢️👨🔧🧰⚙️ RED, WHITE & BOOST! 🇬🇧 |
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13th Feb 2017 11:07pm |
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| benniferj Member Since: 20 Oct 2016 Location: Basingstoke Posts: 361 
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Cheers guys. It's good to understand it now. Makes sense. I would have gone for a non led board if I'd realised that's how they work. But that's fine, .2ma is no problem. At least I can finish the job today knowing exactly how it's all working.
I love the knowledge in this place and how people are happy to explain what's going on in detail  |
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14th Feb 2017 9:21am |
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| VeeTee Member Since: 06 Mar 2011 Location: Somewhere Posts: 1512 
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Just thinking... If the fuse is blown, and a high amps drawing device is still connected, would not it be possible then that a too high current flows through the resistor and led, may be causing resistor to burn out? Cheers, Vincent 1959 Polynorm 1/4 Ton Trailer, Olive Drab Green (sold) 1970 M416 Military Trailer (Camping Trailer Conversion), Epsom Green (sold) 1975 Series III 88 V6, Light Green (sadly sold) 1996 Defender 110 CSW 300 Tdi, Epsom Green (sold) 2000 Freelander 1 TD4 3-drs, Silver (sold) 2006 Freelander 1 TD4 5-drs Facelift Automatic, Tonga Green (sold) MySite |
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14th Feb 2017 11:15am |
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| MadTom Member Since: 10 Sep 2013 Location: Olomouc Posts: 573  
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No. The resistor is designed to limit the current for LED when it is shorted to ground. There is no way, how the current can be higher. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo
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16th Feb 2017 9:00am |
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