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1977 Series 3 Headlight Issues


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I have recently purchased a 1977 Series 3, my first Land Rover, and am having issues with the headlights. One works fine, the other is very dim when swiched onto the headlight function. To try and remedy this, I have bought a new switch (needed anyway), two new headlights, and have cleaned up both of the earthing points on the car (one from battery to bottom of engine block and other from starter motor to the chassis). I've followed some advice on forums regarding the earthing etc but have now hit a brick wall.

If anyone could offer some help on this subject it would be much appreciated, I am a complete novice at this!

Many thanks,


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Does the full beam on that side operate at full brightness? That would probably confirm that you have a good earth / 0 volts from the headlamp

You need to ensure that you have a full voltage across the bulb - so as well as making sure (as you have) that there is a good earth (that's the 0volts side), you also need to be sure that you get the full 12.5 - 14 volts (depending on engine off or running) at the other side of the bulb.

So check the feed wires going to the lamp, if necessary all the way from the new switch. Open any bullets and clean with an abrasive like emery cloth or sandpaper. Bright usually means good contact; dull means not so good. In a bullet connector you need to clean the socket part as well which is harder than the plug.

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If one of the lights is bright, then the fault is in the wiring for the dim light. I would suspect corrosion in the connectors or frayed wiring entering the bullet ends, but it is possible that you have a broken wire on a vehicle that age, with only a few intact strands. Find the fault as a matter of urgency; poor connections overload the spot that is conducting, making it behave like a filament and getting very hot - it is almost as likely to start a fire as a short circuit.

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Just re-read your initial post.

You talked about checking the main earths but it's more likely that it's either:

1. The +12 volt feed to the lampholder (as mentioned by Snagger and in my earlier post)


2. It could be the local earth - the one near to the lamp unit itself. Find that connection (to the body somewhere) and check that it is bright too.

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The easiest way is a process of elimination - run a temporary replacement earth wire from the dim bulb to a good earth. If that doesn't work, run a length of wire from the Lucar connector (where the wire from the switch splits for each light under the slam panel). Once you identify the failed wire, replace it. Better still, get a few meters of the right coloured wires from vehiclewiringproducts.co.uk (you could just go to a local autofactors if you don't mind using wrong coding plain coloured wire - I'd suggest plain white for substituting the blue with white trace and red for the blue with red trace), all run with protective wrap and grommets through the wings, to replace the old wiring outright. 8A wiring for the individual runs to the lights will be ample, 17A if you replace the wiring from the switch to the connector.

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  • 3 weeks later...

Wire the light switch to a relay so that bulbs are switched directly from 12v supply,

The contacts on the switch are pretty crummy and you loose a volt or thereabout.

Same for high beam.

Halogen bulbs will imorove matters.

The sealed units are pretty poor but are only necessary if you plan to go wading through very deep h2o.

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