Defender headlights aren't great compared to modern vehicles (but don't get me started on those piercing white lights...), so a frequent upgrade that owners seek is to upgrade the headlight wiring with a relayed wiring loom. The full power normally passes through the headlight stalk switch, which can sometimes melt, and with other loom connections there can be an unnecessary voltage drop on the entire circuit.
There are a couple of options available on the open market that work by using the existing headlight connectors to switch multiple relays by taking a feed directly from the alternator/battery. However, the options I found didn't fit my (demanding) requirements: 1. I didn't want wiring to pass in front of the engine or by the radiator, 2. I didn't want any relays in the engine bay. This is if something goes wrong I can investigate inside the vehicle and to stop them having to cope with the weather. Call me stubborn, but it meant the only option was to make a custom headlight loom.
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The power feed is taken straight from the battery to two relays (one for dipped beam and one for main beam) which are mounted in the battery box.
The relays have integral fuses which makes the wiring a lot simpler. The separate main and dipped cables travel unbroken direct to the bulbs. The relays are switched by the left hand headlight connector by using a
male H4 connector. By using the existing headlight connectors, the loom is totally "plug and play", so if it develops a problem, I can easily switch back to the factor setup if required. The earth cables all return direct back to the battery also, ensure the least voltage drop possible. This is a compromise for having the relays outside of the engine bay, as the best positive feed would be directly the alternator.
The difference was quite good, as two of the photos shows where I wired the LH headlight to the new wiring and left the RH headlight on the old wiring (dipped and main beam). It seemed to make a difference when driving in the dark initially, but having used this for a few years, the dipped headlights don't really seem to be that great - it's probably just their design limitation. Main beam is really good however. LED headlights is not something i'll be looking at as they are not very cost effectve.
