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Headlight Switch Burning Out


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Hi All,

Having issues and need your help!! <Please accept my apologies if there is already a thread on this - I have read a number of threads but could not find any that quite covered this issue - if you know of one please let me know>

I have a 2000 Td5 Defender 110. I had my headlights fail suddenly whilst the Landy was at attack speed on the motorway (think back country road in the UK for equivalent quality road) and on an extremely dark night. Typical. Anyway suddenly in pitch black I threw out the sea anchors and after very nearly filling my pants I got her to a stop. Lucky for me I was not mid way through a high speed turn otherwise I would not be here to write this post. Well lucky for me at least.... :)

The side lights still worked but no headlights. By pulling back on the control column I regained full beam.

Anyway I bypassed the switch (connected all three wires together) and problem solved so carried on.

I replaced the headlight switch and I thought the problem was solved.

About 12 months later this happened again. Luckily this time I was parked in town. So no underwear change required this time so improvement on one level at least ...

I did notice a clicking sound behind the dash with the faulty switch on.

Luckily I had kept my "bypass switch" and I have been using that for sometime now with no issues other than the faf of having to plug it in rather than flicking a switch.

Anyway I thought it was about time I get this problem solved before I fit the new headlight switch that is making the trip over from the UK as I write this. I know nothing about electrics so I had my Defender at the auto electrician last Friday.

He could not find out what is causing the switch to burn out. He was going to add a relay? In the circuit but said there was already one there so he was stumped. Does he need to add a different relay or could the one be faulty or does he need to and another? Or is the relay not the issue?

I have replaced the head light bulbs with a brighter bulb but I would need to check with what as this was a while ago (it is midnight here in the colonies so can start pulling the headlights to pieces tomorrow if you need to know). I am about 80% sure the first switch failure was with standard bulbs and the second was with the brighter bulbs. But I cannot be certain sorry.

As I say it is the final stage of the headlight switch that is burning out - the first stage (side lights) work.

Other info:
I am also having the #8 10 Amp hazard light / rear wash/wiper fuse blowing - is this related in any way? My auto electrician came up with nothing there too!
The three wires in my "bypass switch" get quite warm when in use - not sure if this is significant or not but include just in case.
Looks like my Auto Electrician needs some guidance so any help would be very much appreciated!!!
If you need any more info please let me know and I will find out for you.
If I can't get this solved I suggest we all buy shares in Lucas given the amount of headlight switches I will be buying!!!
Thank you in advance I am really stuck here. Appreciate it. Big time!
Cheers
Scotty.
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If you uprate the bulbs (higher wattage) you give the already poor headlight switch a hard time, I know you say they are relayed currently, but I would check this, you may find the relay is something to do with driving lamps or something unrelated...

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If extra driving lights such as spots are fitted then these need a separate relay, result of not doing so is a melted light switch. If you have as you've indicated, uprated the original headlamp bulbs with a higher Wattage then this may have the same effect and the standard relay being not heavy enough to handle the extra current. If the standard relay has failed, open it up and see if there is any evidence of scorching or the components having melted or welded together, if it has then there's your answer. Modern vehicles are now fitted with an extensive array of relays, one or more for practically every circuit. Without the vehicles wiring diagram it's sometimes very hard to locate some of these relays as they're tucked away behind panels, trim and all sorts of unimaginable places

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The headlamp switch is really quite a bad design: for a start, the full headlamp-current passes through the switch: also, the wires are soldered to small tags, but these are then riveted to the switch-contacts themselves *through the insulated base of the switch*.

Which means the riveting can't be done with the sort of 'industrial-strength' amount of clamping pressure you really need.

Over time, the rivet-to-tag contact's resistance rises, causing corrosion, causing higher resistance, causing more corrosion and eventually the whole mess melts itself.

Also, the moving part of the contact assembly is a small brass "horseshoe" in a nylon housing, with a small spring behind it to provide contact pressure. Any poor contact here generates heat, softens the nylon and then when the switch is put back to 'off' the nylon hardens, sticking to the horseshoe and meaning that in future the sprng doesn't provide any worthwhile pressure on the contacts.

"High-power" headlamp bulbs just draw more current making the time-to-switch-failure shorter. A proper relay-setup will relieve the main headlamp-switch (and the normal/dip switch) of the tens ofamps the bulbs take.

--Tanuki

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Hi there - huge thank you to you all for your help I appreciate it!!! Cheers!

I will pass it on to the auto electrician for further investigation and let you know how i get on! I finally found another thread on this topic: http://forums.lr4x4.com/index.php?showtopic=60245

Just on this note does anyone know what the relay is for behind the instrument panel? It is down low, in the back right hand corner behind the instrument panel. It is "clicking" when I cycle the faulty switch through its full movement so wondering if this could be related or causing any problems possibly? I have a photo but not sure how to share that with you.

If this head light switch is notoriously poor has anyone just fitted a heavier duty switch? Apart from being a real faf my "bypass" switch has worked faultlessly so was wondering with my huge lack of any knowledge :) if this would work.

I am also wondering if anyone has any ideas why the #8 10 Amp hazard light / rear wash/wiper fuse is blowing at regular intervals - is this related in any way?

Thanks again for your help. Really appreciate it...

Scotty

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I'm not at all familiar with later Defenders but for what it's worth, on the Defender 90's where the fuse box is situated on the bulkhead behind the gear lever and shrouded with the cover, the fuses and relay contacts were very prone to forming a powdery corrosion which causes fuses to blow at random, removing fuses and relays one at a time and giving the terminals and sockets a squirt of electrical cleaning fluid helps and if that doesn't work suspect the relevant relay that controls that part of the circuit.

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In my experience with towing and in the context of this subject, my number 1 tip would be to plug and unplug the trailer lighting connection with the Land Rover lights and engine turned off, if you don't then be prepared to re-fit a few fuses!

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The relay behind the clocks down on the right is the dim / dip relay. A red herring here I expect.

My switch burned out - I replaced it with a pattern part - which also burnt out - so I wired the three wires together as you have done ....

Which must have put too much load through the wiring and resulted in a plastic header further 'down stream' in the loom melting and me losing the lot.

The header was a dash out job - a really pain.

My Td5 was 10 years old when the first switch burnt out - so after the pattern part burnt out in short order I then bought a genuine switch (I'd avoided it for the cost the last time) and its been fine for 3 years and counting.

It's a poor design as said above .

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Thank you! Mike - might look at taking your advice and rewiring it as per your instructions once and for all given it is such a poor design. Phil - was not towing at the actual time the switch blew but I do tow reasonably regularly so guess could of played a part in this. Thanks for the info and tips everyone!!! Got to love LR's.... You have all been a huge help. Will get onto it and try and get this sorted. Thanks again I really appreciate it! Scotty

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