Historic Vehicle Authority of New Zealand

The Vintage Car Club of New Zealand


Andrew McClintock trys to throw some light on the weighty subject of lighting for your Vintage or Veteran vehicle.
this article was first published in Beaded Wheels issue 265 December/January 2003

If you consult the VIC VINTAGE REPORT on page 12 of Beaded Wheels 262 you will see that the VCC now have headlight endorsements as part of the ID card condition. A daylight use only is clearly explained as in condition C. It is condition B that concerns me. There should be very few club vehicles that can’t meet the normal WOF requirements. There are a lot of new rules for moderns but the rules for older vehicles haven’t changed since 1976. Transport Regulation 1976 states dip beam is to illuminate the road and substantial dark objects 50 metres in front of the vehicle. However a light meter is now being used at WOF time to establish that your lights will comply with that rule and your lights will now have to be in as new condition to comply. I would hate to think any of our members would apply for condition B simply because they didn’t want to repair their lights. Remember you will be restricted to 30 kph and will be passed by bicycles, mopeds and power-cycles as these vehicles are exempt from WOF testing and won’t need an ID card even though their lighting wouldn’t comply. By the way don’t be tempted to try and keep up. Remember if you exceed 61 kph you risk instant loss of licence on the spot. For that reason alone it is important to do all you can to keep your lighting up to standard.

It may seem a little simplistic but there are only four reasons why your lights may not be as good as when they left the factory. They are:
1 the reflectors and lenses,
2 focus,
3 alignment
4 voltage at the bulbs.
The lenses need to be the original type that were supplied with your reflectors. Some replacement lenses had a pink or yellow shading in the glass so try to find lenses made of clear glass. Your reflectors are very important. They should be re-silvered and in pristine condition. The silver oxidizes with exposure to the air. They need re-silvering about every ten years. I have not had a lot of luck with repolishing reflectors. It is very easy to polish right through the silver. I now only wipe them with soft mutton cloth. You can use a silver cloth as you would use on household silver. If using a polish it must be non-abrasive such as Mothers Metal Polish or you can place your reflectors in water with an anode as you would with antique silver ware.
Keeping air and dust off your re silvered reflectors is important. Replace the cork or rubber seals, but don’t use RTV silicone sealer as it gives off a gas that reacts with the silver and turns it black.
The focus and alignment of your lights is essential. Follow the procedure explained in the Repair and Restoration Technical Manual on pages 55 and 56 – Permanently dipped lights should drop four inches in ten feet. Some lights have a focus screw in the centre at the back of the headlight shell. Replacement pre focus bulbs of dubious manufacture can be poorly made, if in doubt about the focus try another brand. You shouldn’t touch the glass on halogen bulbs, but if you have, wipe them clean with meths on a soft tissue before you turn them on.
Disconnect your battery before making any alteration to wiring.
Vehicles that are going to be a problem are Dodge Fours, Hupmobiles and other American cars with single filament bulbs and a resistor in the light switch for dip beam. You will need to re wire and fit double filament bulbs. Any vehicle with a sloping lens e.g. Morris Eights, VW Beetle, Chrysler, Dodge, Ford V8 and others, up to 10% of your light is lost due to refraction on the lens. All you can do is make sure everything else is in order.
On motorcycles with flywheel lighting coils, re magnetize the flywheel and be sure to fit the recommended bulb or a lower wattage bulb. Never fit a higher wattage bulb.
Model Ts with 18 volt magneto and nine volt bulbs in series vary a lot with engine speed. Make sure you use the correct bulbs, check wiring, reflectors, switch, magneto coils and re magnetize. It is essential with the Model T and lighting coil motor cycles to have the engine running at speed when testing your lights. This is a good idea with any vehicle. Any increase in voltage will improve your lights.
If all the things discussed so far are attended to and you have voltage drop your lights will still not be working properly. When my grandfather’s house was changed from gas lighting to electricity he could not understand how they could get all that power through such tiny pipes. Well that could be the problem with your vehicle especially if it’s six volt. Restriction in the pipes, oops sorry, wiring. Electricity behaves like water. You need pressure (volts) and volume (current measured in amps). When you water the garden a shorter large diameter hose will supply more water at a better pressure than a long smaller hose. Kinks or damage to the hose will cause resistance to the flow of the water reducing both the pressure and the current (volume). Resistance in old wiring and connections will reduce the voltage and the available amps (current). Water won’t flow unless there is more pressure at one end of the hose than the other and it’s voltage that makes electricity flow. To water your garden you put your finger over the end of the hose or fit a sprinkler. This increases the pressure but if you fit too big a sprinkler it won’t work properly due to pressure drop. The answer is a bigger hose. Bulbs are measured in watts. The higher the watts the less resistance like a larger sprinkler, so fitting lower wattage bulbs increases the pressure (volts) and gives you brighter lights. Best to fit the wattage recommended by the manufacturer or lower if the correct ones are no longer available. Higher wattage bulbs will give you brighter lights but only if you can keep the voltage up. Voltage drop in the wiring ammeter, light switch, dip switch etc will result in a duller light and and heat at the high resistance point. Put your hand on the ammeter terminals with the lights on and you will see what I mean. It’s a common problem area. Clean the terminals and nuts and make sure they are tight. The only resistance you want is the bulbs. There is no doubt that higher wattage bulbs will give you better lights if you can supply the amps (current) or volume of electricity to maintain the (pressure) volts.
A number of vehicles are being fitted with alternators. In my opinion this is not the answer. Firstly it’s no longer original and secondly an alternator is no more efficient than a generator at the same rpm. The advantage of an alternator is it can be run up to 10,000 rpm and more without damage. A generator would disintegrate long before that. Most alternator conversions I have seen seem to be running at the same speed as the old generator. You can’t fit a small enough pulley with the wide belts on older vehicles. If your generator has a fan built into the pulley it will cope with higher wattage bulbs. Early non-ventilated third brush generators may overheat. Don’t risk burning out your generator, a re-wind is expensive. As a rough guide if you have six volt 24 watt bulbs, coil ignition, park lights, dash lights and tail lights your generator will need to put out about ten amps. If you change to 35 watt bulbs with the same additional circuits you will need about 15 amps. Few original ammeters are accurate. Use a quality separate ammeter to check your vehicle. Motorcycle generators, starter generators, Lucas generators with off-set armatures and one field coil, and Veteran era generators can only cope with the original wattage bulbs. Regardless of whether you use the original size or larger bulbs you can suffer voltage drop. A practical test is simpler than using a voltmeter. To test I use two light weight jump start cables, turn your highbeam lights on, fit one jumper lead to your engine block and the other end of the same lead to the bulb holder or reflector. If the light comes up brighter you have a faulty earth. This is a common fault and often overlooked. Now take the other jumper lead and connect it to the live battery terminal. Be careful not to touch the other end on any metal parts of your vehicle. I clamp a small Philips screw driver in the free end and use it as a probe. The probe is then touched on the live bulb terminal. If there is a noticeable increase in brightness there is voltage drop in the circuit. If you get the wrong terminal both filaments will come on and the light will be brighter. Use a light board and it will be obvious if you get it wrong.
If you have voltage drop the simple cure is a headlamp relay. (Relays are not practical on motor cycles, you will need to use a voltmeter to establish where the voltage drop is and repair it.) A relay is simply an electrically operated switch. You now have one switch (the relay) instead of two (the light switch and the dip switch) and heavy and shorter wiring. Purpose built relays are getting hard to find. Second hand ones are ok but make sure the voltage is correct. You can use two 30 amp modern relays but the wiring is not as neat.
Mount the relay as close to the lights as practical. I always solder the terminals. Crimp terminals can give trouble with the amperage required. The old instructions recommended the power supply to the relay came from the live battery terminal but I recommend you run the supply wire to the alternator output terminal, or the cut out, or voltage regulator live terminal.
This will give you one or two volts more than the battery voltage when the charging system is working. It makes a difference. The bulbs can handle it. Six volt bulbs are in fact rated six to eight volts and 12 volt are 12 to 14 volt. If you have trouble with bulbs blowing it will be high resistance between the charging system and the battery. (A loose ammeter terminal, battery terminal or similar.)
The size of wire you use is important but before I get onto this it is important that we are comparing apples with apples. There are a number of ways to measure automotive cable. The old way was to count the number of strands. They were and still are .01″ or .3 mm. Six volt head lamp wire was called 40-012 (forty strands of twelve thou wire). 40-012 is now referred to by quality cable manufacturers as 3.00 mm2. Cut price cable suppliers refer to it as six mm. They apparently measure the outside diameter of the insulation but over the years the insulation, has got thinner and it’s not even six mm anymore. For that reason I will refer to a New Zealand reference number as used by Hamal Cables and others. If in doubt strip back and count the number of strands. It doesn’t cost a lot more to use heavier wire than you need and avoid voltage drop. For 12 volt systems use New Zealand ref (154) 3.00 mm2 40-012 from the relay to each head lamp and for an earth from the reflector back to the engine block. (I always recommend separate earth wires whether you need them or not.) For the supply wire to the relay you need 80-012, this size is hard to get and expensive as it is a slow moving product, so use (158) 8.00 mm2 96-012, it’s bigger than you need but cheaper.
For six volt use (156) 5.00 mm2 65-012 to each light and earth and (158) 8.00 mm2 96-012 to supply the relay. Even fuses can cause voltage drop so use a 50 amp fuse, fuseable link or circuit breaker in the supply wire. Some relays have fuses built in and won’t need a separate fuse.
Your local auto electrician should have the wire I have recommended and will be able to tell you how to wire up your relay. If in doubt get them to do the job.
You can also improve your lights with quartz halogen bulbs (see the advert in Beaded Wheels classifieds) but to get the best out of them make sure you attend to all the other things in this article first and don’t try a higher wattage unless you understand and have attended to possible voltage drop.

Text Andrew McClintock Cartoons Barry Way

Disclaimer: The author and the Vintage Car Club of NZ Inc. take no responsibility for any loss, damage or cost incurred in following these instructions.