Headlight Power

[Chlorate]

A while ago I had a rather inconvenient loss of all power going to my headlights in the Xantia, which lead to me overstaying my welcome at Thurrock services (but that's another story).

Turns out that even though there was 12v arriving at the light stalk, there must have been some hefty resistance somewhere down the line meaning nothing could be powered.

It was fixed by running a couple of lengths of 1.5sq.mm wire from the battery and splicing it in. For whatever reason I hadn't managed to fix the high beams (so all I have are sides and dipped).
So my question, can I be lazy and use the same bit of wire that powers the side lights to power the high beams as well, or would the combined draw too much current for that particular thickness of wire?

[myglaren]

Might pay to do the relay mod and get the very best from your lights while protecting the switch/wiring.

[Xantidote]

Going right back to square one, according to my BoL, the headlights and sidelight are all powered up though maxi fuse "D" (engine bay). I assume you've checked this?

Could you be more specific about where you spliced the 2 temporary wires into the circuitry.

[Chlorate]

It was literally a case of working backwards from the switch with a multimeter. Working out which pins in the socket needed a new 12v supply cutting those wires and soldering in new ones straight to the battery.
First thing I did was to check for common fuses etc. with all the stuff that also didn't work (i.e. headlight washers, dashboard lighting etc.) the only thing that was common to all of them, apart from the big D fuse which a lot of other things also go through, was the switch itself.

What is this relay mod you speak of, what does it do?

[myglaren]

What is this relay mod you speak of, what does it do?

Instead of the current for the headlights being routed through the ignition and light switches, this supply only operates relays.
The relays, located as close to the headlights as possible, draw current through over-dimensioned wires either from the fusebox or directly from the battery terminal and thus to the lights.
It has the added benefit that there is less of a voltage drop in the wiring, so the bulbs receive the full 12V and the brightness increase is well worth the effort.
If drawing directly from the battery you would need fuses in the lines - some relays come with a blade-fuse socket integral.

For precise instructions on how to do this, there are some posts covering it as several members have performed it and been very satisfied with the results - Xac being one IIRC.
Was going to do it on my C5 but never seem to get round to it.

[Chlorate]

I was quite surprised they didn't do this anyway. Seems rather daft to have a few amps going back and forth through the indicator stalk.
I'll have a butchers, you can pick up mini fuse and relay boxes for very little money.

However in the mean time, back to my original question
To get my high beams working again can I power both the side lights and the high beams through the same bit of 1.5sq.mm wire?

[Monkeyfeet]

I've done this on Xantias and it was always worth it. But I used 2.5mm. Make sure you use multistrand, that's plenty flexible enough. (1.5 is a bit weedy really). Think I've even done 1 wire per circuit feed as you asked.
Mentioned already I know but: If you're going straight to the battery stick in an inline fuse/s close as poss to the battery terminal. Source of volt drop and corrosion I know but I've seen what can happen if the relay it's supplying gets corroded and short circuits itself......