NicTheOrange90 Posted February 6, 2010 Share Posted February 6, 2010 Im looking to mount an LED light (like flourescent strip) in the Defenender. Done this before on other vehicles, but this time Id like to get a feed from the existing factory light switch. Fitted the new LED, put live and earth above headlining. Removed existing switch/light and found: 1x earth on a backplate 2x live feeding the switch (both mainly purple). I put a meter on the copper strip on the back of the unit and to my surprise it seems the lamp has 12v all the time .... (yes I did have the door closed etc). copper strip #1 goes from purple live to the switch copper strip #2 goes from another purple live to the festoon lamp, then carries on to the switch silver strip #1 goes from the switch to earth The switch has three positions: ON - er as it says Middle - operates with the door opening and stays on for xx seconds afterwards Off - dont come on at all. My assumption is that the switch somehow disrupts the flow to earth and thats why the copper strips both seemed to be live... (bulb was not lit until either switch set to ON or door opened). So - Can I get a 12v supply for the LED that is switched from the central light unit ? We have them on vehicles at work and the LED gets its power from the left [passenger reading] of three units inthe roof Discos and Shoguns ane even 5 series Beemers. I can always run a 12v supply and switch it, but looks neater without a second switch. Can a grown up who knows more about interior light switches give me a quick dummies guide please? Quote Link to comment Share on other sites More sharing options...
western Posted February 6, 2010 Share Posted February 6, 2010 IIRC it's switched by the earth, when the door switch is operated [door open] the switch earths to the body/light switching it on. connect the led lights power to the existing power purple/blue wire & it's earth to the existing lights earth, hopefully it should work. Quote Link to comment Share on other sites More sharing options...
NicTheOrange90 Posted February 6, 2010 Author Share Posted February 6, 2010 Thanks Ralph, Sadly its too dark to try now, but Ill give it a go in the morning. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted February 6, 2010 Share Posted February 6, 2010 Yes, the interior light is switched on the ground side. The door pins short straight to their mounting screw when the door is opened. If you just want to add extra lighting, switched as the standard lamp, just add the extra lighting in parallel, making sure wire/fuses are appropriately sized. Quote Link to comment Share on other sites More sharing options...
NicTheOrange90 Posted February 7, 2010 Author Share Posted February 7, 2010 OK, didnt go according to plan.... Already had earth into the earth for the light, so took a feed from purple/white, it had the following results Light switch in position OFF = 1 small LED lit (ie a small current getting to LED), no festoon Light switch in position CENTRE - LED on full (door closed/engine running/not running) festoon very dim Light switch in position ON = 1 small LED lit (ie a small current getting to LED), festoon on If I had the switch in the CENTRE position, and door open, Festoon on, no LED.... A tad confusing... I see from the wiring diagram that the purple/white gets its feed from the ECU.... I wonder if its a current draw thing... so it might work properly If I replaced the festoon with a fusible link? Alternatively I might just wire up a separate switched supply...... ( have the switches, just wanted to make it neater). BTW the LED is a 42 LED unit so probably draws a little more current than a small LED unit... Quote Link to comment Share on other sites More sharing options...
errol209 Posted February 7, 2010 Share Posted February 7, 2010 OK, didnt go according to plan.... Already had earth into the earth for the light, so took a feed from purple/white, it had the following results Light switch in position OFF = 1 small LED lit (ie a small current getting to LED), no festoon Light switch in position CENTRE - LED on full (door closed/engine running/not running) festoon very dim Light switch in position ON = 1 small LED lit (ie a small current getting to LED), festoon on If I had the switch in the CENTRE position, and door open, Festoon on, no LED.... A tad confusing... I see from the wiring diagram that the purple/white gets its feed from the ECU.... I wonder if its a current draw thing... so it might work properly If I replaced the festoon with a fusible link? Alternatively I might just wire up a separate switched supply...... ( have the switches, just wanted to make it neater). BTW the LED is a 42 LED unit so probably draws a little more current than a small LED unit... Errrr... The existing light has two "feeds". The purple and white is the live from the rest of the car (on mine this comes off a fuse in the usual place). The straight-to-the-roof black wire is used as ground when the switch is in the "always on" position, and the other mainly-purple wire is the one that goes to the pin switch on the door(s) and is used as earth when the switch is in the "on when the doors are open" position. To do what you want a) don't replace the festoon with a fuse, it or your ECU just go pop and b) you really need to connect your LED unit accross the festoon contacts. 42 LEDs at 40mA each is just over 1.6A, so this could be straining the ECU. The diagram below shows what I think you need to do ... The extra diode under the festoon bulb is to stop a feed going the wrong way to the ECU, but this diode can be a one amp (tiny) thing. If lower level guidance would help, please shout. Quote Link to comment Share on other sites More sharing options...
smokinv8 Posted February 7, 2010 Share Posted February 7, 2010 If lower level guidance would help, please shout. I laughed my head off at this quote! Thats just the sort of level that I need!!! Quote Link to comment Share on other sites More sharing options...
errol209 Posted February 7, 2010 Share Posted February 7, 2010 I laughed my head off at this quote! Thats just the sort of level that I need!!! HTH! Seriously tho', its a fine balance between egg-sucking lessons, patronising and being helpful sometimes Quote Link to comment Share on other sites More sharing options...
NicTheOrange90 Posted February 7, 2010 Author Share Posted February 7, 2010 Could I replace the festoon with an LED festoon to reduce the current draw ? Also there are loads of diodes around please can you give me info on what I need ? there a quite a few 12v diodes on eblag. Quote Link to comment Share on other sites More sharing options...
Andrew Chua Posted February 8, 2010 Share Posted February 8, 2010 i found this out the hard way. i actually wire-ed parallel lamps to the middle and back of the interior from the front light. works well and is still working. i've halogen down lighting. nice romantic orange lights. yes, the current drawn is about 2amps. but one day while cleaning the td5 90, i opened the cover at the back on the right side and i found the connector for the rear interior lamps. so if you are looking for them, it might be worth a try there first before you pull wires all the way from the front. they are always 'on' 12v. so you can find it even without the engine running. yes, it's the purple black one. Quote Link to comment Share on other sites More sharing options...
NicTheOrange90 Posted February 8, 2010 Author Share Posted February 8, 2010 on my 110 the rear light operates by itself if you open the rear door, and side doors operate interior light at the front. If I can just get a bit more info on what type of diode we need, Im sure things will be fine... Quote Link to comment Share on other sites More sharing options...
western Posted February 8, 2010 Share Posted February 8, 2010 from errol's reply above The extra diode under the festoon bulb is to stop a feed going the wrong way to the ECU, but this diode can be a one amp (tiny) thing. Quote Link to comment Share on other sites More sharing options...
NicTheOrange90 Posted February 9, 2010 Author Share Posted February 9, 2010 Thanks for that Ralph, I did read the description about the 1amp, but when I search on ebay for 12v diode, and there are loads, so I try to refine the search by adding 1amp, but then there are none. They all seem to be listed with their wattage rating and no mention of amps. Dont want to get the wrong part. Perhaps I should just stick to putting it on its own switch and fused supply as I obviously need the 'lower level guidance' Quote Link to comment Share on other sites More sharing options...
western Posted February 9, 2010 Share Posted February 9, 2010 if there's a Maplins in your area try there for diodes of that amp rating. or via thier website http://www.maplin.co.uk/Search.aspx?criteria=1amp diode&menu=-2 Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted February 9, 2010 Share Posted February 9, 2010 Thanks for that Ralph, I did read the description about the 1amp, but when I search on ebay for 12v diode, and there are loads, so I try to refine the search by adding 1amp, but then there are none. They all seem to be listed with their wattage rating and no mention of amps. Dont want to get the wrong part. Perhaps I should just stick to putting it on its own switch and fused supply as I obviously need the 'lower level guidance' Watts divided by volts gives amps unless it's different for diodes ? Mo Quote Link to comment Share on other sites More sharing options...
errol209 Posted February 10, 2010 Share Posted February 10, 2010 Watts divided by volts gives amps unless it's different for diodes ? Mo Are you sitting comfortably? Diodes are semiconductor junction devices, and have a "forward voltage drop" of around 0.6v, which means that if you measure accross the two leads you'll see a voltage of 0.6V (though this varies between types and rises slightly with increasing current). So, at one amp a smallish silicon diode (the commonest) will generate I x V = Watts of heat, or ~0.6W. Being cautious, I'd specify a diode with a bit more current capacity, and a power rating based on the current rating times 1 (lots of factor of safety, and only pence). However, most diodes are rated to a current, and this takes account of the power thing. These ones are a good choice, 1N5400 is 50V reverse rated (plenty) and only 23p, or these (1N4001) for 16p (but not proper pointless over-engineering in true LR tradition) Quote Link to comment Share on other sites More sharing options...
errol209 Posted February 10, 2010 Share Posted February 10, 2010 Could I replace the festoon with an LED festoon to reduce the current draw ? Yes. Quote Link to comment Share on other sites More sharing options...
Andrew Chua Posted February 10, 2010 Share Posted February 10, 2010 pardon me, but am i missing something here? why do you even need the diode? the ECU was designed to switch 2x 10W loads for the interrior lamps as each is a 10W bulb. Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted February 10, 2010 Share Posted February 10, 2010 Are you sitting comfortably? Diodes are semiconductor junction devices, and have a "forward voltage drop" of around 0.6v, which means that if you measure accross the two leads you'll see a voltage of 0.6V (though this varies between types and rises slightly with increasing current). So, at one amp a smallish silicon diode (the commonest) will generate I x V = Watts of heat, or ~0.6W. Being cautious, I'd specify a diode with a bit more current capacity, and a power rating based on the current rating times 1 (lots of factor of safety, and only pence). However, most diodes are rated to a current, and this takes account of the power thing. These ones are a good choice, 1N5400 is 50V reverse rated (plenty) and only 23p, or these (1N4001) for 16p (but not proper pointless over-engineering in true LR tradition) Come along Errol, time for your medication and then back to the nice, warm, soft place Mo Quote Link to comment Share on other sites More sharing options...
errol209 Posted February 11, 2010 Share Posted February 11, 2010 pardon me, but am i missing something here? why do you even need the diode? the ECU was designed to switch 2x 10W loads for the interrior lamps as each is a 10W bulb. I made the assumption that the ECU output was solid state rather than relay switched and then erred on the side of caution. I don't know my way round the ECU, so I'm not going to suggest a solution that might blow it up! If the ECU output to the interior light is relay switched then you do not need the diode at all. Come along Errol, time for your medication and then back to the nice, warm, soft place Mo Look, the goverment pade for my edewkation and isle be dammed if I are going to let it goe to waist! Quote Link to comment Share on other sites More sharing options...
The Badger Posted February 17, 2010 Share Posted February 17, 2010 easiest way is just replace the festoon with one of these - easy ( think it's that size) I did it and it works fine, nick you can see it if you are passing my shed at any point, also you can give me a quote for some networking. Quote Link to comment Share on other sites More sharing options...
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