Bit of a newbie question....

Hi guys,
I have a classic car, British, with Lucas (The Prince of Darkness) electrics.
Now, in an attempt to get a bit more light than the standard Lucas lamps provide (To quote a motoring journalist, 'a pair of copulating glow worms produce more light"), I have fitted a set of four new Cibie units, two H1 high beams and two H4 high/low beams. Bulbs are 130w H1 and 90/130w H4.
I understand that the standard wiring puts all the power for the lights through an old Lucas 3 position rocker switch (Off/sidelights/on) that has caused many an old Brit car to go up in flames. My question is: Do I need to protect this switch alone with appropriate relays, or both that AND the dip switch? Also, in terms of length of cable run, is the distance from switch to relay the critical one, or from relay to light bulbs?
If anyone could advise me what gauge cables, type of relays (and how many) I should be using, that would be fantastic! Oh, and a wiring diagram if possible?
thank you in advance!
Jorrocks.

PS. I am fitting a 140 amp alternator producing 90 amps at tickover, so I think I am ok in that regard.

Jorrocks said:

I understand that the standard wiring puts all the power for the lights through an old Lucas 3 position rocker switch (Off/sidelights/on)

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That's "Off/Flicker/Dim".

Those grossly-overwattage bulbs are going to have lower filament luminance and worse focus than their high-quality standard-wattage counterparts.

Using a quality set of relays takes the brunt of the load off the 3-position switch, but you still want to make sure you have appropriate fuse protection for the switch *anyway*. I'm not sure what the wiring looks like in that particular car.

Usually one uses a set of relays for each beam pair (one for the lows, one for the highs, another for an auxiliary high beam set).

This is a good resource for how to do your relays, and even if you don't order the relays and sockets from Daniel Stern, heed his advice-- your safety depends on using quality components that won't leave you in the dark.

Welcome to the board here!

Very, very important, first thing, right this minute, go and remove those 130w and 130/90w bulbs from your car. Seriously, do it IMMEDIATELY, before you turn on the headlamps again. Installing them was that big of a mistake. At best, your car's headlamp circuit was designed for 60/55w H4 and 55w H1 bulbs. Depending on what year and model the car is, it might have been built with a circuit configured for less than that -- like 45/40w high/low and 50w high. And given how "classic" is another word for "old", the circuit's capacity is less than it started out. Your high-wattage bulbs are a giant overload on the circuit. The immediate effect is uselessly dim light, but you are actively headed for extensive and expensive vehicle damage (electrical fire). Throw the high-wattage bulbs in the trash; even with an upgraded circuit they are not a good or effective way to improve your ability to see. More about bulbs later.

I have fitted a set of four new Cibie units, two H1 high beams and two H4 high/low beams.

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Good choice. With appropriate bulbs, those are good lamps.

I understand that the standard wiring puts all the power for the lights through an old Lucas 3 position rocker switch (Off/sidelights/on)

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"Off/flicker/dim", as the old joke has it.

Do I need to protect this switch alone with appropriate relays, or both that AND the dip switch?

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Protect both switches and put full power to the lamps by installing relays in accordance with this guide.

Now back to the topic of bulbs: it's a mistake to put in high-watt bulbs (and it's illegal if your car was first used in the UK on or after April 1, 1985). High-watt bulbs, even if they are adequately served by large-gauge wire and relays, do not really improve your ability to see. They put out more light, but they also have physically larger filaments which de-focus the beam pattern from the headlamps. Most of the extra light hits the road close to the car (the foreground) rather than in the distance. This makes it feel like you've got great lights, but your seeing distance range is much shorter than it should be. Take a look at this post for comparisons. Put in Philips Xtreme Vision +130 bulbs (55w H1, 60/55w H4).

Then, find a shop that is willing to aim your headlamps reasonably. It's hard to find such a shop in the UK and throughout Europe, where a twisted and misinformed notion of "safety" causes many shops to aim the lamps far too low. They think they're maximizing "safety" by minimizing glare, but they're not. The UK MOT specifies that the low (dipped) beam cutoff must be between 0.5% and 2.75% below horizontal for a headlamp mounting height of up to 85cm above the road surface. Many shops tend to set the lamps at 1.3%, 1.5% or 2% below horizontal. That is far too low for adequate seeing distance range at ordinary road speeds. Find a shop that will set your headlamps at 0.7%. That's within the MOT tolerance, still enough drop to insure against glare (dazzle) to other road users, and it will give you much more adequate seeing distance range. To put numbers on it, the low beam cutoff of headlamps mounted 60cm above the road surface will reach out to:
30 meters in front of the car if aimed 2% down
40 meters in front of the car if aimed 1.5% down
46 meters in front of the car if aimed 1.3% down
60 meters in front of the car if aimed 1% down, and
86 meters in front of the car if aimed 0.7% down.

Thank you both for your replies, very informative! I hadn't actually installed the HiPo bulbs as I am on standard wiring at the moment. I will follow the advice re. the Philips bulbs, I assume that if they're being fed a good 12 volts then they're going to perform considerably better for that reason alone.

Jorrocks said:

I assume that if they're being fed a good 12 volts then they're going to perform considerably better for that reason alone.

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12V is abysmal. 12.8 is absolutely the barest minimum; you'll want more along 13.2V.