Member Since: 31 Jan 2009
Location: Filey
Posts: 430
Guide: Wiring your own spot lamps / driving lights
Okay, admittedly not the hardest thing in the world to achieve. But, not wanting to break into the main beam wiring unnecessarily, I wasn't really happy with any previous solutions.
My system will give you the option of switching the driving lamps to one of three settings. A) off all the time, B) on all the time, or C) on whenever the high beam is used.
Time for install after making loom: 3 hours
Difficulty: Electrical experience required
1. build yourself a loom
Power cables should be in 4mm sq. wire, but you will need to split these out into 2 x 1mm sq. wires for the last bit of run to the LR connectors (1.5mm sq. wire can be used on the connectors at a push). The LR spec connectors, type 'Econoseal 2 way female 0-012-42' can be purchased from John Cooper & Sons, Yeadon, leeds (do a google search). £6.25 for a pair of connectors inc. P+P. Obviously these can still be used if not using the LR spot lights, but remember to buy the male ends of the connector as well if this is the case. Using the correct connectors will give the wiring loom a more ‘factory’ finish rather than your typical bodge job rubbish of twisting wires together and the like. Sorry no part numbers for the relays / fuse holders as I already had these kicking around.
The wiring diagram I devised is as follows:
Click image to enlarge
The diagram maybe easier to see if you open it up from within my gallery. I should really have measured the lengths of run to make it easy to be copied – but I didn’t so you’ll have to get you’re measuring stick out. Remember the control wire (0.5mm SQ will do the job) needs to be long enough to run from the battery box, to the spare battery box to wherever you are mounting the switch.
2. Install the under bonnet section of the loom
Fit the wiring as shown, ty-raping the conduit behind the diagonal braces behind the grill, locating the connectors low down.
The relay is secured behind the battery, pos and neg to the battery terminals. Run the 0.5mm controlling wire with the existing vehicle cables in the little conduit below the windscreen, to the spare battery box. In the spare battery box, low down on manual vehicles there is an unused grommet. I think with automatic vehicles you will have to go through the bulkhead with the existing cables. At this point I decided to run a host of cables through for any future needs, but this is only to cover future plans on my part.
Looking from the inside of the vehicle, up behind the accelerator pedal with the kick panel removed you will be able to locate the other side of the grommet, hiding behind the rubber backed foam, here I cut some away to get access:
3. Interior wiring
Again refer to the wiring diagram and remove the 'knee' panel and steering column cowling. Locate the indicator stalk wiring and tap into the Blue/White wire and the Blue/Red wire with some new wires. Somewhere in the cable run from this point to where the light switch will be mounted solder in the two diodes as shown on the diagram - effectively the two wires now become one. Add this to the wire coming from under the bonnet; along with a negative wire sourced by connecting to the earth stud behind the RHS kick panel (or taken from one of the pins on the light unit), gives you the 3 wires required for the switch. Run these in a tidy manner to their final destination, which for me is around the light switch area. Here I added a 3 pin connector but this is not essential.
4. Fitting the Switch
Remove the switch surround (grey section) by lifting at the bottom first, giving it a firm pull. The switch unit screws will now be visible. Remove these screws, and disconnect the wiring plug as you withdraw the switch unit. The front face plate of the switch comes off using a screwdriver on the tabs.
There is a space in the switch unit just big enough for a 20mm switch (mine is from seller 'mobilecenter' on ebay, approx £2 - make sure it is an on-off-on type). Carefully mark and drill your hole for the switch, also drill a small hole for the wires to come out of rear of the switch assembly. You won't be able to use crimps due to the limited space, soldering is the only way.
The wire that originates from under the bonnet will go to the middle pin, the earth wire to the top and wire from the stalk switch to the bottom. These positions are correct for most switches, Here is my finishes modified switch unit with the three pin connector visible at the rear:
And fitted:
.
Test out the operation of the switch / wiring and re-fit all the panels, admire your handy work.
Last edited by Iain G on 16th May 2010 10:36 pm. Edited 5 times in total
My only comment, is that I would personnally use thicker cable for the supply to the lights. Before I sold my Defender, I'd put some spots on the front and used 6mm from the battery, via a separate fuse to the relay and then the lights. Overkill, but minimum volt drop.
Mind you, I obtained the wire from work Mark.
2006, D3 SE Auto - gone but not forgotten.
2014 BMW 530d M Sport Tourer.
1977 Triumph Spitfire 1500
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15th May 2010 9:25 am
Martin Site Admin and Owner
Member Since: 06 Nov 2004
Location: Hook Norton
Posts: 18460
Great write up Iain, thanks for sharing
Have edited your posted slightly to link to the full size wiring diagram - hope that's ok.
I think you have a slight error on your wiring diagram, the on-off-on switch should be the other way round I think?
Like this:
Click image to enlarge
06 D3 SE / 15 LR D90 XS SW / 88 LR 90 Td5 / 68 BMW 2000 ti
Any issues with the site let me know!
I've just noticed on the new diagram, that you are suggesting a 30A fuse to the lamps.
With 1.5mm cable that is too big - should be max 15A and then you'd probably burn out the cable before the fuse blew (Fuses will pass the rated current). I would use a 10A fuse with 1.5mm cable or 15A with 2.5mm cable.Mark.
2006, D3 SE Auto - gone but not forgotten.
2014 BMW 530d M Sport Tourer.
1977 Triumph Spitfire 1500
_________________________________________________
Disco Picture Website Here
15th May 2010 10:33 am
Martin Site Admin and Owner
Member Since: 06 Nov 2004
Location: Hook Norton
Posts: 18460
Mark, I don't know if by "new diagram" you mean mine, but I've not changed the fuse rating, only the switch 06 D3 SE / 15 LR D90 XS SW / 88 LR 90 Td5 / 68 BMW 2000 ti
Any issues with the site let me know!
Well, I didn't look too closely at the diagram before - your changes have made it easier to see
But whatever, the fuse as shown with 1.5mm cable is way too small. But the principle is fine.Mark.
2006, D3 SE Auto - gone but not forgotten.
2014 BMW 530d M Sport Tourer.
1977 Triumph Spitfire 1500
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Disco Picture Website Here
15th May 2010 10:41 am
Iain G
Member Since: 31 Jan 2009
Location: Filey
Posts: 430
OK, to clear up a few pointers.
Firstly the switch is shown correctly on the diagram - the signal wire from the relay goes to the switch common terminal.
Secondly the voltage drop. The lamps consume around 10A each. Therefore given a 5' length of cable from the battery to the lamp, doubled to take into account of the return run gives an impedance of around 0.04ohms for the 1.5mm sq. wire, equating to 0.4 volts dropped. This volts drop to me is fine given your battery is sitting around 14V with vehicle running, and this volts drop is comparable to the vehicles other lamps.
Thirdly, with reference to current carrying capacity, the LR spot lamp wires are around 1mm sq. And I struggled to get 1.5mm sq. into the connectors due to the limited size. Obviously you can run the loom in something like 4mm sq. (or even 6mm sq. as mentioned above), and split your thinner wires from the thicker 4mm sq. close to the spot lamp connectors.
All valid points, but routing your cables correctly and running them in conduit will almost eliminate the chance of short circuits to chassis.
The cable, as you say, is fine - its only my opinion (primarily dating back to many years ago when I had a 6V VW Beetle - and 0.4V was too much!)
And yes, routing the cable correctly will minimise the risk of shorts - but 1.5mm cable is still only rated at 16A - and the section from the battery to the relay is drawing 20A ish. There is a risk of it overheating (Yes I know its unlikely, but I wouldn't want to take the risk.)
With reference to the LR spots - I would guess they are 55W bulbs? In which case the current draw is about 4A per bulb - which is fine for 1mm cable, which from memory can carry about 10A
Interestingly, if you use tri-rated cable, then 1.5mm can safely carry 21A. But it will run hot.Mark.
2006, D3 SE Auto - gone but not forgotten.
2014 BMW 530d M Sport Tourer.
1977 Triumph Spitfire 1500
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Disco Picture Website Here
15th May 2010 10:10 pm
Martin Site Admin and Owner
Member Since: 06 Nov 2004
Location: Hook Norton
Posts: 18460
Iain G wrote:
Firstly the switch is shown correctly on the diagram - the signal wire from the relay goes to the switch common terminal.
Morning Iain - as your diagram is drawn operating the driving lamp on-off-on switch either connects the relay coil signal line to ground via the main beam/flash switches or it connects ground to the anode of the diodes Whereas in my mind it should be grounding the relay coil signal line to do what you've said (permanently on)?
However, I'm happy to pull my diagram if it's only going to cause confusion 06 D3 SE / 15 LR D90 XS SW / 88 LR 90 Td5 / 68 BMW 2000 ti
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16th May 2010 10:10 am
Iain G
Member Since: 31 Jan 2009
Location: Filey
Posts: 430
Angelfire - I did state to run the cables from the battery in parrallel, this included to the relay. It was just so that anyone making the loom didn't have to go and find umpteen sizes of cable. Your current draw from the battery does sound right, and I may of actually fitted a 20A fuse - I will amend my drawing to show this, so thanks for spotting it. I will also recommend a cable size of 4mm to as close to the spot lamps as possible, before breaking out into 1mm for the short run for the connectors.
Martin - To elaborate on the diodes, the arrow indicates the flow of conventional current. Therefore the current flows through the relay, through the spot lamp switch if in the 'auto' position, through one of the diodes depending if full beam or 'flash' is used, to the gnd connection on the indicator / full beam switch, therefore completing the circuit. Also to clarify the switch has more than two positions, being an on-off-on type means you have the third switch position which will turn the lamps off at all times.
16th May 2010 6:26 pm
Martin Site Admin and Owner
Member Since: 06 Nov 2004
Location: Hook Norton
Posts: 18460
Iain, I'm not doubting the function of the diodes
I believe that in the "permanently on" position, the wiring diagram as you have it can't make the required circuit to do that, there's no earth path given to the relay. Mentally flip the on-off-on switch in your diagram and trace the route of the earth connected directly to that switch - it routes down to the column switches instead of to the relay coil.
I'm sure you've wired it as in the diagram I put up though 06 D3 SE / 15 LR D90 XS SW / 88 LR 90 Td5 / 68 BMW 2000 ti
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Whereas in my mind it should be grounding the relay coil signal line to do what you've said (permanently on)?
