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| revd Member Since: 20 Apr 2024 Location: England Posts: 153  
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Similar problem to me, new left hand stalk and light switch solved the problem, bought Land Rover Genuine parts from Rimmer despite the astronomical cost rather than be hostage to fortune with aftermarket. Dim-dip was UK only requirement, but with Land Rover who knows? - the relay is behind the speedo on rhd. If you are having a reoccurring problem even with new (good quality) switches then a poor earth or short somewhere is the likely cause, maybe even a rodent?
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7th Jan 2025 2:31pm |
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| 4RF RDS Member Since: 19 Jul 2015 Location: Ottawa Posts: 950  
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What you are describing sounds like a dodgey/intermittent ground somewhere... suggest you reestablish ground wires for the headlights.
Good luck 2010 Range Rover MkIII Autobiography Super Charged (Idris) 2003 Range Rover Mk III (Desmond FitzWilliam) 2000 Defender 110 CSW TD5 (CTX) 1992 Range Rover Classic (Lizzy) 1972 Series III 300 Tdi (Stanwood) 1967 MGB GT Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats. H. L. Mencken (1880 - 1956) |
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7th Jan 2025 4:08pm |
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| bujango Member Since: 07 Jan 2025 Location: Tours Posts: 6  
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Thanks for your reponse, revd. Were the contacts in your switch sunk in from melting ? Could you visually constate the damage? Thanks for the heads-up re: dim-dip, was ready to strip the whole front end looking for it! |
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7th Jan 2025 9:21pm |
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| bujango Member Since: 07 Jan 2025 Location: Tours Posts: 6
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Thanks for your responsd 4RF RDS. When I installed the boomslang I regrounded both front headlights. I also took out all the side lights and cleaned all contacts.. Are there other grounds i should be looking out for ? The thing that drives me bananas is that it everything is operational when I replace parts, but then suddenly the problem arises again… As the boomslang install looks good still (tested again today), but plugs into the old wiring in order to operate the switch, it would seem that the problem would be between switch and headlights.. but then again why did it work so well after the initial install ? |
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7th Jan 2025 9:32pm |
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| revd Member Since: 20 Apr 2024 Location: England Posts: 153
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main switch was visibly ok, but was probably the 2006 original and as I was replacing the left hand column stalk - which even before it left me to drive home on dim dip one night had a habit of switching off the lights for a fraction of a second when flicking from dip to main - so I thought it better to replace both together. Have you checked for loose pins/chafed wires in the various multi-pin plugs? |
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7th Jan 2025 10:31pm |
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| bujango Member Since: 07 Jan 2025 Location: Tours Posts: 6
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Thanks, revd. Just cleaned up the bullet connectors, had some mud so was hopeful, but no dice. Cleaned up grounds again just in case. Not sure what to do anymore.. perhaps I should draw new wiring back from the left headlamp to the switch? The boomslang plugs into the original wiring.. if I rewire that last bit perhaps i’ll have a functional totally parallel system.. wish I could find the actual problem and fix it !
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8th Jan 2025 6:08pm |
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| revd Member Since: 20 Apr 2024 Location: England Posts: 153
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If all else fails I would remove existing wires and make up my own headlight loom from battery to lights via the switch with all crimped connections etc
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8th Jan 2025 7:05pm |
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| Navigator11 Member Since: 07 Jan 2025 Location: Gloucestershire Posts: 3 
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I started a very similar thread on the technical section; my problem is slightly different because my lights go off but then come back on, but I have done much the same as you. Looking at the wiring diagram there is a header joint, which I believe is behind the dashboard. I have read somewhere about possible problems with it, though where one gets a replacement goodness only knows - call for Wagos?!. Hence my plan when the weather gets a bit warmer to take the dash off, search wires for any bad connections, shorts etc. Then I plan to take wires direct from the light switch to the boomslang relays (via a fuse of course). This will bypass the existing relays. Fingers crossed
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9th Jan 2025 5:31pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20529
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Check there is voltage on the headlight fuse in the LR factory fuse box, and that the fuse is secure and the female housing behind is okay.
You should be able to put the multimeter set to voltage check ground probe to a good chassis ground, ideally the battery ground post, but a clean solid chassis ground will do. Then the live probe on each pin on the top shoulder of the ATO fuse pins. With the ignition on you should get voltage there 12v approx on both, if just one then the fuse is gone, if the voltage is very low or fluctuates moving it, it might be loose. A sporadic fault of coming and going, is likely high impedance so a loose ground, or terminal, fuse, crimp connector etc. Remember the live side is only half the circuit, and also depends on where you test and take your ground from. If you isolate everything, you can continuity test, both the live side and ground side. Set the multimeter or Ohms, touch the probes together to read 0 Ohms, it’ll likely beep as well. You can test continuity in the circuit, both live and ground side, ideally isolate all circuits first, by testing from point A and point B. The reading you are looking for is as low and as close to Zero as possible, if the reading is high then there is likely the location of the loose connection, switch, contact, or break in the circuit between point A & B. Keep an eye out for water in or around any fuse boxes or relays, that can cause a lot of problems. A high impedance circuit, will have a lot of voltage drop. So if it should be 12.2v, you might see 4v. As close to zero ohms that you see is low impedance, which is what you want to see, some resistance is normal. So it won’t be completely zero but near, and variable. High impedance is not ideal, and is normally a sign of the fault., and location. So using this you can trace the location of the problem, on both sides of the circuit by doing that in a comprehensive progressive way. You can add a temporary ground with a test lead also, and small croc clip test leads can be very useful, just beer in mind they are small gauge and designed only for testing, not carrying load for any tine due to small gauge plus they have some resistance themselves they add to the circuit. My guess is, the LR side is most likely culprit, not the extra additional loom. I’d look at the stalk connections and pins most, even if new, loose connections are common there. Corroded or loose connections are a common reason for high impedance, which can produce low voltage on ignition, but when the engine is running with alternator voltage the extra 2v approx, overcomes the high impedance in some some circumstances, but not all. Temperature also has an effect, which is why things can change with heat causing expansion and cold causing compression, when warmer some electrical connections expand and become more loose, some with the couple of volts extra improve and resistance decreases. I would get the existing LR headlight plug behind the headlight. Check the ground resistance between the ground pin and a chassis ground, if it’s way off or high impedance it is a ground fault back, if it looks fine. Test the dipped pin, and main beam pin for voltage. If one shows low, and the other normal it’s one of those circuits, most likely dipped. Use a ground thats chassis ground, not the H4 headlight plug ground. If you identify one of the three, you can then concentrate on that particular feed, and work back to its source, which you may find a small reel of a few meters of say 1mm2 thinwall useful as the multimeter test leads might (likely) will not be long enough, in combo with some croc clip test leads can be very useful. If you do this with a live, you can simply put a 10A fuse in an inline holder nearest the power source end if you want to, just means if you accidentally shorted the power then the fuse would go. For identifying the fault location, continuity checks are more useful and safer whilst isolated / turned off. So once you’ve done a few voltages tests I’d isolate all the power, either from the battery or pulling the fuse(s). Then you can turn the switches on and off, without any power present, no risk of draining the battery due to load, or any accidental shorts etc. Turn off the interior lights whilst working on it, if you don’t isolate the battery, especially in cold weather as if you have something running, like interior lights or headlights, over time it will draw the battery down before you know it. If everything checks out on the LR side, then it’s the headlight loom, bear also in mind that some headlight looms are wired up differently. You always want a plan B, mine has 3 circuits and 3 independent relays, one for dipped, one for main and one for aux spots / light bars. This way, if you lose dipped you always have main beam, and if you lost main, you’d have dipped. You don’t want to be driving along anywhere and have lights out if there was a fault. There isn’t a Relay on the LR wiring as standard, all load goes though the main lighting switch and then stalk contacts, which is why it’s a good idea to fit an aux headlight loom as the current load is significantly reduced though the switch contacts, plus there are various benefits. Another Multimeter test you can make is find a good chassis ground up front near a headlight, and attach the ground probe, set the multimeter to voltage check. Start engine, and identify the LR H4 headlight plug and also a headlight loom plug. Turn on dipped in the LR. Test the dipped pin on the LR side, if the voltage is below 10v say then the fault is on that circuit. If that checks out as normal then plug the tap side back into the LR wiring, and test the Headlight loom side, if the voltage there is below expected then it’s the headlight loom side. Beware handling the headlights, they easily slip out of your hands, don’ adjust the beam angle screws, leave those screws well alone. You may be able to reach from behind and leave them in situ but is a bit more tricky. Failing all of this, pull the dim dip resistor, under the drivers side wing on a RHD, it’s an Econoseal connector. It causes more problems than it’s worth. No Guts, No Glory. 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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9th Jan 2025 7:58pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1431 
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IIRC somebody had issues with the relays on boomslang loom. Either sticking poor earth or corroded, I can’t really remember ….
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9th Jan 2025 8:44pm |
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| miker Member Since: 13 Sep 2015 Location: Surrey Posts: 1768 
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Probably the splice joints in the dash, I've been suffering with a very similar fault. Need to pull the dash to check for sure, but my suspicion is it's corroded or otherwise disintegrating
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9th Jan 2025 11:20pm |
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| bujango Member Since: 07 Jan 2025 Location: Tours Posts: 6
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Thanks everyone for all the insight.
Custom90 thanks very much for the method, now I have a good starting point and some exciting weekend plans. Hopefully will be back here with good news by saturday afternoon! |
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9th Jan 2025 11:45pm |
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| MadTom Member Since: 10 Sep 2013 Location: Olomouc Posts: 632  
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Get the rigth version of electrical schematics, some multimeter and start checking, from batery, throught fuses, connectors, switches to the lamps.
LR likes connector headers to connect multiple wires into one circuits. They are tiny, burried behind the dash and prone to corrode and/or burn. I had to cut the off and solder connect the right wires instead. No more problems. Defender TD5 and Discovery TD5 use the same type of headers and suffers the same problems. With help of electrical schematics you can find, what connector/switch/fuse/header you have to look for, in electrical library there are pictures, descriptions and placement in car. Check all header you will find, not just those in light circuits. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo  |
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10th Jan 2025 7:51am |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20529
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Tracing by following wiring schematic is very useful, so long as you can find the exact one and no alteration.
Let us know how you get on, if you put a few notes down you can tick off the list as to where you have checked. You can even find, though not that common a wire has a split in the sheath aka casing that’s hairline, moisture gets in and corrosion, or the conductor inside has split too but looking at it you’d barely see. But enough to cause high impedence under load and voltage drop. The same with connectors etc, just one loose, but visually looks okay is enough to do it. The connections on the stalk are very common for it, as the main lighting switch has the lighting circuits going through it too. So a lot of people think the main beam stalk is just that, main flash or locked, but it’s not only, it has the dipped as well going though it IIRC. Just the main dipped and sidelight switch is the switch but those circuits, at least the dipped goes though the stalk as well. If a female housing is loose on a pin or pops off then there is an issue straight away. I had it, new stalk, all was good fitted it, didn’t work despite testing before fitting. During fitting one of the female connectors was loose and came off. Luckily this is why I always test before putting cowling back etc, I found it, slightly tightened the connector and refitted and it’s been perfect since. Often the contacts in the stalk or switch also burn due to load over time, get bent or otherwise degrade. A lot of that is because the load goes through them all, which is why people fit an aux headlight loom. Which reduces the load through the switch from 9Amp approx to around 200mA (0.2Amp). Which significantly extends its life. If you do use say Wipac Crystals it also improve voltage drop as it picks up the supply direct from the Alternator and with a shorter cable run with lower impedence which means the current is slightly lower, but the voltage peak performance at the headlight. Still backwards and forwards compatible with LED also, the reduced current via switchgear is beneficial across the board.  No Guts, No Glory.
🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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10th Jan 2025 12:41pm |
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