Headlight relay mod ? wiring diagram for 3CL/Jota?
- Thread starter cape
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Dellortoman
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- Tasmania, Australia
sfcpiet said:
I was planning to clean my teeth with it
I would use heavier wires from the relay to the battery. I always use a dual core insulated heavy wire. Not sure what gauge it is but it would be at least twice the diameter of the red and black wire shown here. The ground wire I terminated on the bottom left corner of the RGS headlight frame which has a metal stud there, then grounded every thing else to the same stud, the relays, the headlight and even took a ground wire from there up into the instruments to stop all the ground fluctuations there. Things like the neutral light getting brighter and darker with the indicators flashing etc all got better suddenly with a good ground.cape said:And to the garage I go...
Great photo which relay helps to explain it.
Cheers''Derek
Dellortoman
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Warning: Technical content. Suitable for nerds only.
2.5mm2 copper will carry around 25A before it even thinks about getting warm.
A 100W light draws about 8A at 12.8V, so the wire is well within its current rating.
What about voltage drop? I hear you all shouting ...
Resistance of 2.5mm2 is 7.4 mΩ/m, which translates to about 0.011Ω for a 1.5m run. At 8A, that's 0.086V drop over that length. Mind you, the length should be doubled (electrons gotta go there and back), so the total voltage drop is 0.17V for the circuit wiring, or 1.4% of system voltage. Not much in the scheme of things.
If you want to get more technical, the energy dissipated in the wiring is around 11 Watts. If your alternator doesn't have 11W to spare, maybe you should think about bigger wire, but otherwise I don't think you'll have any problems.
4mm2 would be overkill. It would reduce your energy loss to 6.5W, but you'd struggle to find room for it in the headlight shell.
Besides, I don't think your headlight filaments will be as high as 100W. 35W/55W (low/high beam) is normal, but I think you can buy 45/65 quartz halogen bulbs that will chuck our a heap of light.
With a typical 55W high beam filament, energy loss in the 2.5mm2 wiring is a paltry 1 Watt. I don't think you're in any danger of setting fire to your wiring harness.
Cheers,
Cam
2.5mm2 copper will carry around 25A before it even thinks about getting warm.
A 100W light draws about 8A at 12.8V, so the wire is well within its current rating.
What about voltage drop? I hear you all shouting ...
Resistance of 2.5mm2 is 7.4 mΩ/m, which translates to about 0.011Ω for a 1.5m run. At 8A, that's 0.086V drop over that length. Mind you, the length should be doubled (electrons gotta go there and back), so the total voltage drop is 0.17V for the circuit wiring, or 1.4% of system voltage. Not much in the scheme of things.
If you want to get more technical, the energy dissipated in the wiring is around 11 Watts. If your alternator doesn't have 11W to spare, maybe you should think about bigger wire, but otherwise I don't think you'll have any problems.
4mm2 would be overkill. It would reduce your energy loss to 6.5W, but you'd struggle to find room for it in the headlight shell.
Besides, I don't think your headlight filaments will be as high as 100W. 35W/55W (low/high beam) is normal, but I think you can buy 45/65 quartz halogen bulbs that will chuck our a heap of light.
With a typical 55W high beam filament, energy loss in the 2.5mm2 wiring is a paltry 1 Watt. I don't think you're in any danger of setting fire to your wiring harness.
Cheers,
Cam
Spider Wales
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"CAM!" I prostrate myself at your Antipodean Feet, how nice to hear someone speak my language across the vast expanses of Oceans!. 
Dellortoman
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- Location
- Tasmania, Australia
That will work OK Pete. If you want to minimise space occupied by the relays, you can use one twin coil relay instead of two separate relays. They're available from most of the usual automotive relay suppliers. The wiring is ecactly the same as you have drawn, the only difference being that both relays are housed in the same box.
Cheers,
Cam
Cheers,
Cam
81Lav
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- Location
- NSW Australia
Here is a photo of my set up on the SFC 1000.
New earth (5m2) and new Pos (5m2) are run back to the Battery earth and Fuse Box respectively.
The Fuse box on the SFC had a spare slot so I just wired that up for the new Battery to Relay connection.
I used a dual relay, as Cam has suggested, which I picked up at an Auto Electricians for $16.
All you need to do is series the +ve to both relays.
Made a big difference to what can only be described as a shithouse headlight.
Cheers
Bruce
New earth (5m2) and new Pos (5m2) are run back to the Battery earth and Fuse Box respectively.
The Fuse box on the SFC had a spare slot so I just wired that up for the new Battery to Relay connection.
I used a dual relay, as Cam has suggested, which I picked up at an Auto Electricians for $16.
All you need to do is series the +ve to both relays.
Made a big difference to what can only be described as a shithouse headlight.
Cheers
Bruce
81Lav
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- NSW Australia
tstrainer
Senior member
- Location
- Honiton, Devon
Cam , if you can get hold of it give a product called Deoxit a try. Bloody brilliant for cleaning oxidised connections. Seems quite expensive fortunatly i "borrow" mine from work..
Gents,
This wiring diagram with relays and Yam switches I've once uploaded to the laverdapedia wiki to the "upgrades"section IIRC.
Contents -> Maintaining -> Upgrades -> 100/1200 Triples 180 -> Electrical-(180-1)
You need to log in
HTH.
Stefan
PS: Sorry, I could not open the attachments function here.
This wiring diagram with relays and Yam switches I've once uploaded to the laverdapedia wiki to the "upgrades"section IIRC.
Contents -> Maintaining -> Upgrades -> 100/1200 Triples 180 -> Electrical-(180-1)
You need to log in
HTH.
Stefan
PS: Sorry, I could not open the attachments function here.