::: Up-rating your headlight wiring loom :::
If you own a Golf, chances are - at some point you'll have found yourself thinking 'bloody hell I can't see a damn thing with these lights'. The main cause of this vaguely dangerous lack of brightness is a 2.5-volt drop between the battery and the bulbs. This is chiefly due to the rather long route the loom takes before it gets to the bulbs. When Andy fitted this loom to his Golf GTi, the voltage at the headlights dropped by only 0.1 volts which allows the full voltage from the battery to get to the headlights. The results are even more impressive when coupled with a pair of Xenon H4 headlight bulbs & a pair of Xenon H3 spot light bulbs (Phillips & Osram bulbs came joint 1st followed by Ring bulbs in a recent Auto Express test).
In a double lamp set-up you can up-rate just the dipped beam, as the extra spots tend to help give an acceptable main-beam. To wire up the main beam & spotlights is the same process as for the dipped beam conversion, only this time you'll have to also cut the wire that has 12 volts when main beam is on, this is the White & Black wire on a 1992 MK2 Golf GTI.
These guidelines are based on a conversion performed on a 1992 8v MK2 Golf GTi but can be adapted for use with other VW's that have this problem.
What do I need?
A Relay with 30-amp switching capacity
All of the above components should be the best possible quality and should be fitted to the highest possible standard! If you have any doubts about performing this conversion you should take your car to a competent Automobile Electrician and have them do it for you.
If your car has dim dip i.e. when the sidelights are on and the engine is running the headlights also glow dimly, you will need to disable this. On a 1992 8v MK2 Golf GTi this is the two yellow wires that come from the coil fitted on the chassis below the headlight. It is about 10cms long and has a white plug that connects near the bottom of the air-box. Simply unplug this. If you don't disconnect the dim dip coil the headlights will light (not dimmed) when the sidelights are on. N.B. You don't need dim dip to pass your MOT.
In front of the battery and behind the headlight you will see the loom that goes to the headlight bulb. Switch on the ignition and put the headlights on (not main beam) now using a test light or multimeter identify the wire that is showing +12 volts, now turn off the lights and check that the 12 volts no longer registers. Mark the wire and repeat this process for the other headlight. This wire was Yellow & Black on a 1992 8v MK2 Golf GTi but may not be the same on all Golf's. (Before proceeding further it is wise to disconnect the battery).
You should now cut these wires leaving enough room so that you can connect to either end of the cut wires. The first wire that you cut (the one coming from the bulb) should now be connected via an appropriately lengthed piece 20-amp wire to terminal 87 on the relay. You can secure your relays in a multitude of ways, an easy one is to cable-tie them to the main battery cable. You will now need to connect another wire to terminal 87, which should then be routed to the other headlight. This wire should then be connected to the cut wire on the bulb side. The other end of wire that you have cut should then be taped back into the loom with insulation tape.
Now the wire that you cut first that does NOT come from the bulb end should be connected to the thinner wire and then connected to terminal 86 on the relay.
Terminal 85 then needs to be connected to a good earth, for example using the spare negative spade on the battery terminal.
Terminal 30 should be connected via a 20-amp fuse to the positive terminal of the battery We would suggest using a ring terminal, as this will give the best connection.
Reconnect the battery.
Your dipped beam should now be considerably better. If you measured the voltage before fitting the loom, measure it again and you should see a good improvement in the recorded voltage at the headlights.
Kindly written by Andy Bryant.
WARNING. These guidelines are for fitting standard wattage bulbs only, if higher than 55/60 watt bulbs are to be used then the wiring, fuses and relays will need to be up-rated accordingly.
Disclaimer : Matey-Matey accept no responsibility for any of the information contained within this document or the accuracy thereof. It is intended as a helpful guide and is solely based on personal experience. The authors also wish to stress that the methods highlighted are centred around personal opinion and there may be other equally credible ways of performing this conversion..