Originally Posted by
AK83
Re the switch: if you ground the two wires whilst the ignition is on, or engine running, it will confirm if the light or an electrical fault is at play. Ign needs to be on at the least for the warning light to come on.
Fuse F14 is where power comes from, but if it's the fuse, you will lose a few other warning lights at the same time. Can't recall exactly, but think oil warning light ... maybe?
If you're under there, there should be two wires to the switch, one black(earth) check it for continuity to chassis to be sure it's OK, and with ign on and diff lock mechanism engaged, check the other wire(unfortunately BLACK and BLUE stripe!) for battery voltage .. ie. whatever volts your battery will be at.
This will at least confirm power to the switch and if the power wire(Black-blue) is grounded the dash light WILL come on. If not either a bulb or other electrical problem down the line.
If the electrics turn out OK, and it doesn't turn on the warning light with the mechanism engaged, then by the sounds of it the internal stuff is not working.
With wheel jacked up and engaged, you shouldn't be able to turn wheel more than a few degrees(due to driveline slack).
So, if this is the case, then sounds like at a minimum remove the side cover plate and see and feel what's happening at the linkages and dog clutch there.
You can remove the spindle cover too(3 bolts) but won't see much from the sides, maybe enough from the top if you have console off, but it could be that the internal arm is not locating correctly into the shaft to move the dog clutch, or arm could be broken, or spinning on the spindle shaft or something.
There are plenty of vids on Utube, my preferred vid makers for LR are Landrover Toolbox and Britannica Restorations .. but any will show you the easy to understand nature of the diff lock mechanisms in there.
So, as an example of what you could try. If you pull the side cover off, and find that the spindle is not moving the arm rearwards, you should be able to manually force the arm rearwards, may have to twist propshaft a little to get gears meshed for the mecahism to engage. If you can do this with the one wheel jacked in the air test, it will confirm for sure if the actual diff itself is locking OK. If you can move the arm rearwards and the diff doesn't lock the wheel in the air, you have more serious issues down the line to the centre diff.
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