Thread: The Easy Defender Headlight Relay Upgrade

This is something I've been meaning to post up for a while.

The headlight wiring in the Defender is terrible - we all know this. From the factory, all of the current for both of the headlights leaves the battery and heads towards the starter motor. At the starter motor, it turns and heads into the cab – through the lighting switch, to the headlight on relay beneath the dash, back through the indicator switch, through a fake relay in the dash near the driver’s door, to the fuses under the dash and then to the lights. It is an unbelievably poor design.

Voltage at the headlight bulbs on my Defer was 10.5V, they may have well have been candles.

I thought long and hard about the neatest, easiest, cheapest way to turn the existing headlight circuit into something worthwhile activating at night. This is what I came up with:



Basically, everything that you need to see is here (ignore the rather poor wiring effort coming in from the top of the image - that's something else I'm working on). To keep the new headlight relays safe and dry, I thought they should go with the others under the dash. To do this, you have two options; buy two more of the standard factory relay holders, or buy ones from Jaycar (P/N SY4078). These units are cheap, stronger than the LR units and most importantly have the same mounting bolt spacing so that they attach into the same spot under the fuse box. For me the Jaycar units were easily available over the counter rather than having to wait for an order to come in for the LR ones, so it was a no brainer. The downside is that you need five of them rather than two LR units to add to the existing ones. The Jaycar ones DO NOT slot into the LR ones.

So, parts required are:
- Jaycar SY4078 x 5
- 5 pin relay (the ones with two outputs or ‘pin 87’s) x 2
- Spade connectors x 4
- Ring lug (possibly, see step 5 below)

Wiring the two new relays – one for low beam, one for high beam – is simple. First, here's the layout of these relays.

Pins: 30 - Power to controlled circuit, 85 - Earth for trigger circuit, 86 - trigger, 87s - outputs. Make sure you don't get relays with an '87a' output, they won't work.

Method:

1) Pull the existing feed for each light’s fuse out of the back of the fuse holder (one for LHS low beam, RHS low beam, LHS high beam, RHS high beam).
2) Cut the connector off ONE low beam supply and ONE high beam supply (it doesn’t matter which side they were), and tape them up neatly so they don’t short out on the bulkhead.
3) The remaining two cables are now the trigger feeds for the high and low beam relays (the input marked 86 on the new relays).
4) Power feeds (pin 30) for the two relays can be wired in from a number of places – the starter motor or battery being the best two spots. Use a cable with an inline fuse, something around 2.5mm2 is fine. Please don’t waste your time with large cables.
5) Pin 85s are all earths – find an appropriate spot to either solder them onto an existing earth cable or make up a few leads with ring clamps on them and stick them on the bolt where the fuse holder bracket attaches to the bulkhead.
6) On the low beam relay, a short (~5cm) lead needs to be made up to jump from the two 87 (output) pins of the relay to the spots where you pulled the feed for the low beam headlights' fuses out from in step 1 (the two 7.5A fuses directly above the new relay). Repeat for the high beam relay.
7) There is no step 7, you’re done.

Now, current for the lights goes from the battery, through the relays, through the fuse and to the lights. Much simpler and my headlights are now easily bright enough – the difference was staggering.

I settled on this solution because nothing has to be changed outside of the fuse box area. Also, there is significantly less stress on the headlight relay (the one that turns the headlights off when the ignition goes off), the headlight switch and also the indicator switch (which is a pricey item if it fails; also a good reason to switch to LEDs).

I have also done a thread on replacing the standard brake, indicator and reverse lights to LED, to finish the job of having your Defender visible at night. See it here.

If you have any questions about doing this, post them in this thread as I'll be able to monitor it easily.

Anyone have the pics from this thread on record? Would like to have a go at this but don’t fully understand with no diagrams, cheers