Loom wiring and overload question

[tallyho]

Wanting to fit a xenon headlight kit and needing to run a new 20A supply I was trying to sus where/how to get this supply. I thought that if I ran it straight from the battery it would have no overload (read short circuit) protection before the fuse. Therefore the wire would need to be capable of handling short circuit current from the battery! On closer inspection it seems that the existing loom supply is also straight from the battery to a fuse box, hence this will not be protected either(from short circuit) as the wiring will not take the full supply current of the battery. Can anyone tell me, is this normal practice? If so I can run a cable straight from the battery for my headlight supply as planned.

Regards

Steve

[KevinW]

I think you'll need a relay to switch that kind of current, and some decent (thick) multi-strand wire.

[wilf]

Yes, but don't. Most cars have no fuse between the battery and the fuseblock, and great care must be taken to avoid chafing etc. of that cable run, or a fire will result. It is not ideal, but is the only way to deal with starter motor currents, which can't economically be fused.

Think about taking your new supply (for the Zenons) off your ignition switch, with an inline fuse to protect that cable run. You will no longer be drawing current for your original headlights, an the Xenons take less current anyway, so the system will be fine if you do it that way.

Alternately, take the supply from whichever fuse currently supplies your headlights.

[tallyho]

thanks guys.
Wilf regarding the current for the xenons - yes you're right that they dont draw as much current as the existing headlights when lit, but on start up they can draw up to 20A (according to the booklet) hence the suggestion of running a new ample supply. Not sure whats in the loom and difficult to check whether it will take this current all be it for a short time. That why I thought a new run directly from the battery to the power side of the relay might be ideal.

Cheers

Steve

[wilf]

A short transient 20 Amps won't hurt your existing wiring, if it was capable of supplying the 12 Amps continuous draw for your old headlamps.

I wired my Xenons as I suggested earlier - they work just fine. The extra feed from the ignition switch is just for the dip/main controller, not the inverter packs, which take their current from the original headlamp circuit. About 5 Amps contnuous, after the initial striking current.

[tallyho]

Originally Posted by wilf

A short transient 20 Amps won't hurt your existing wiring, if it was capable of supplying the 12 Amps continuous draw for your old headlamps.

I wired my Xenons as I suggested earlier - they work just fine. The extra feed from the ignition switch is just for the dip/main controller, not the inverter packs, which take their current from the original headlamp circuit. About 5 Amps contnuous, after the initial striking current.

Cheers Wilf, out of interest what fuse size have you got in your headlight cct? Did you leave the original in which I presume doesn't blow due to the transient high current.

Cheers

Steve

[wilf]

Blowed if I can remember - likely that that circuit is fused at around 20Amps.

[tallyho]

Phew job done - xenons fitted and working. Just one slightly annoying thing, side lights on all time (is this a requirement - safety), yellow side light bulbs and bluish xenons - yuk. Seems that the column switch leaves the side lights on in every position. I suppose its not noticable when all the bulbs are similar colour. Does anyone else have this? Does anyone know if there are any blue side light bulbs to try and match them up?
If they are not required to be on all the time i suppose i could fit a relay to switch them off when main lights are on.

Steve

[wilf]

Can't see the sidelights on mine when the headlights are on - they are just nowhere near as bright!

[demus]

Not sure if any help guys, but you can buy some fairly hefty fuses from here:

Vehicle Wiring Products Ltd. Suppliers of auto electrical parts.

I fitted a 200amp fuse near my battery in the boot, to protect the main cable under the car, then a fuse box at the front running the original supplies, lighting circuits, alternator and ignition circuits etc.
The 200amp fuse holds the starter with no worries so probably could be smaller, would only blow with a complete short.

Cheers,