Quality Cable for Headlight Mod

[MidLifeCrisis]

Thinking of doing the headlight mod (relays near the headlights; dedicated cabling from battery to lights etc).
I'm trying to find a source for 3 core, 35A cable - 1 wire for high beam, 1 wire for normal, 1 wire for foglights.
But all I seem to be able to find is twin.
Anyone got a decent source or do I just need to order single core wire and bundle it up myself (would rather not!)?
I was hoping to use a single cable (with the 3 wires inside) to keep things looking neat?

Also as a side question - what is the best route to get the cable from battery to lights - is it obvious when you start crawling under there or is there a secret/preferred method.

Cheers for any help.

[CJH]

I only ran two cables (no foglights), but I made up my own 'twin core' by feeding a couple of cores down a PVC sleeve (much harder than it sounds, btw).

I used two cores of CM4 from here, and a length of 8mm sleeving (S8 from here). You could probably get three cores down the next size up (S10), but if you give them a ring they'll try it for you just to be sure. If it's at all tight, get the next size up.

As for routing the cable, I managed to get both cores and the PVC sleeve through the grommet that's already in the base of the battery box, and then just fed it along an appropriate route underneath, zip tying as I went and avoiding moving parts. It pushed up very easily to the OS headlight. I then used more of my home-made twin core to get across to the NS light, zip-tying to the existing cable run in the channel below the grille.

[MidLifeCrisis]

I only ran two cables (no foglights), but I made up my own 'twin core' by feeding a couple of cores down a PVC sleeve (much harder than it sounds, btw).

Thanks CJH - just the answer I was looking (other than not having a source for the 3-core) - and I agree - I made up a cable recently by stuffing 2 wires into a sleeve (maybe 3 metres long) and it was a real painful experience using coathangers, bit of wire and swearing - was trying to avoid repeating that!!

Any idea roughly how long the run is from the battery to the lights?

[CJH]

I bought 6m to be on the safe side (and managed to get all 6m down the sleeve - the trick in the end was to get someone to pull the sleeve taught). I've got at least a metre left over, and the run from one headlight to the other used about another metre (I'll check both of those this evening), so at a guess I'd say 4m is safe for the main run.

[MidLifeCrisis]

Thanks - that's all really useful information .
Might just have to bite the bullet and order the single wires and make up my own cable then ...

[CJH]

Out of the 6m of cable that I bought I've got about 1.5m left. It takes about 1.5m to go from the relays to the NS light and about 30cm to go from the relays to the OS light, so that means I used about 2.7m to go from the battery box to the relays.

[MidLifeCrisis]

Out of the 6m of cable that I bought I've got about 1.5m left. It takes about 1.5m to go from the relays to the NS light and about 30cm to go from the relays to the OS light, so that means I used about 2.7m to go from the battery box to the relays.

Perfect - thanks!

[bigherb]

There is not much point in replacing the wires to the headlamps the original power cable is more than adequate, 16A cable carrying 5A not really a problem. Intercepting the earth wires and earthing them close to the headlamps halves the cable run and halves any voltage drop.
The main problem has always been the voltage drop through the ignition/headlamp and dip switches.

[California Dreamin]

There is not much point in replacing the wires to the headlamps the original power cable is more than adequate, 16A cable carrying 5A not really a problem. Intercepting the earth wires and earthing them close to the headlamps halves the cable run and halves any voltage drop.
The main problem has always been the voltage drop through the ignition/headlamp and dip switches.

On a four light 'square lamp' model, the two outter H4 lamps use a 55/60 watt bulb. On full beam the 60 watt elements in the H4 bulbs come on at the same time as the two inner H3's, so thats 2 X 60watt = 120watts and another 2 x 55watts = 110watts 230watts total.
4 seperate elements, so close on 20 amps for full beam operation.

I've not looked at the wiring diagram for the wire ratings but from memory they certainly don't look very heavy, 1.5mm2 or 2.00mm2 at best. Certainly in the case of the 4 lamp version I would say that this was border line at best.

2 lamp versions are a different matter at 10amp draw.
The original wiring isn't redundant as it works well as a 'SWITCH' for the relays.


Martin

[bigherb]

There is not much point in replacing the wires to the headlamps the original power cable is more than adequate, 16A cable carrying 5A not really a problem. Intercepting the earth wires and earthing them close to the headlamps halves the cable run and halves any voltage drop.
The main problem has always been the voltage drop through the ignition/headlamp and dip switches.

On a four light 'square lamp' model, the two outter H4 lamps use a 55/60 watt bulb. On full beam the 60 watt elements in the H4 bulbs come on at the same time as the two inner H3's, so thats 2 X 60watt = 120watts and another 2 x 55watts = 110watts 230watts total.
4 seperate elements, so close on 20 amps for full beam operation.

I've not looked at the wiring diagram for the wire ratings but from memory they certainly don't look very heavy, 1.5mm2 or 2.00mm2 at best. Certainly in the case of the 4 lamp version I would say that this was border line at best.

2 lamp versions are a different matter at 10amp draw.
The original wiring isn't redundant as it works well as a 'SWITCH' for the relays.


Martin

It's still only 9 amps running through 16A cable.

[CJH]

There is not much point in replacing the wires to the headlamps the original power cable is more than adequate, 16A cable carrying 5A not really a problem. Intercepting the earth wires and earthing them close to the headlamps halves the cable run and halves any voltage drop.
The main problem has always been the voltage drop through the ignition/headlamp and dip switches.

So is there a better way to avoid this voltage drop through the switches than replacing the wires and just using the existing wiring as a relay switching circuit? I did this recently, and the difference was quite dramatic from the driver's seat. This photo shows the difference between the new wiring to the OS light and the old wiring to the NS light - if anything it's more marked in real life.

It's still only 9 amps running through 16A cable.

Yes, although this online calculator shows that even 4m of 2mm2 cable trying to pass 9A at 13.85V will drop about half a volt. It doesn't explain the 2V drop that I measured with the existing wiring (I guess that's down to the switches etc), but the same length of 4mm2 cable (for instance) will drop about 0.2V, rather than 0.5V.

[bigherb]

Yes, although this online calculator shows that even 4m of 2mm2 cable trying to pass 9A at 13.85V will drop about half a volt. It doesn't explain the 2V drop that I measured with the existing wiring (I guess that's down to the switches etc), but the same length of 4mm2 cable (for instance) will drop about 0.2V, rather than 0.5V.

4m will stretch nearly the length of the van the headlamp wiring from the fuse box to the headlamps is comparatively short around 1mtr and 2mtrs the voltage drop is negligible in comparison to the voltage drop through the switches.

[CJH]

I was assuming the two-way route from the fusebox to both lights. For a van that's 1.5m wide I don't think that'll be far off 4m. But I agree, the drop through the switches is the bigger problem. So back to my other question then - is there a better way to avoid the drop through the switches than bypassing them altogether?

[bigherb]

I was assuming the two-way route from the fusebox to both lights.

That's why I said earth the lamps on the body close to the lamps.
The easiest way is to just connect the relays into the cables from the dip switch just before they enter the fuse box.

[Oldiebut goodie]

Thinking outside the box for a moment - how about boosting the voltage to the bulbs instead. Could be easily done cheaply if your voltage is around 12 to 13v to start with, a 10A voltage converter (per headlight) could push it up to say 15v giving you room for a 2v drop to 13v. (They need to boost over 1v approx) Just a thought. I don't know what voltage headlight bulbs are rated at but I would have thought that 14.5v would be the minimum. Up for discussion!