I have been tracing a fault where the diff lock light will not extinguish. The diff lock is disengaged. This the reverse of most faults I have found written up!
I removed the switch and this operated in a sense I understand, where it is normally open and if you press the switch at the end, it closes the circuit and buzzes out on my multimeter. So with the switch in my hand and ignition on, I press and the light remains illuminated on the dash. I tried shorting the wires in case the switch was doing funny things, but the dash light stays on.
So I traced the wiring back to the bulkhead. I disconnected the wiring that runs from loom to the switch. Connected my multimeter and it showed open circuit on each wire until I shorted the bulkhead end and it buzzed out fine. I also totally disconnected the wire to the switch from the bulkhead end and no change.... light still on. So I don’t think that wire has broken down due to age and is causing issues.
So I am thinking it’s from bulkhead to light where the issue is. Has anyone a wiring diagram or any suggestions? I have 12v to the switch and the light on. Is it a relay and we have an issue? Just a really irritating light to have on all the time!
Not saying this is your problem but the diff light staying lit is a known issue. Try this simple fix if the diff lock light won't extinguish just drive backwards a short distance and it should release the spring-loaded locking collar and the light should go out.
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I have jacked up a wheel and tested to see if the lock is engaged. It isn’t. That’s why I removed the switch and stared to trace wiring. Closing or opening the circuit with or without the diff lock switch in the circuit doesn’t change the light status.
This happened to me last week after getting bogged dropping off firewood. It stayed on for about half a mile when I had to reverse it turned off. It bothered me while it was on but haven’t thought about until I read this
^^ That will be due to the difflock dog clutch taking a while to spring out and disengage, and is fairly normal, it is certainly not a fault (unless it is so stuck, usually through lack of use, that is never disengages). The warning light is activate by the dog clutch itself rather than the linkage, so will continue to indicate the locked state until the dog clutch moves.
Familymad's issue is definitely an electrical issue of some kind, not a mechanical issue, since it manifests itself with the switch disconnected and with the operation of the switch simulated. It is almost certainly either a broken wire resulting in a permanently open circuit or a short to ground, depending on how the switch is configured on his vehicle.
“ So with the switch in my hand and ignition on, I press and the light remains illuminated on the dash. I tried shorting the wires in case the switch was doing funny things, but the dash light stays on. ”
But what does diff light do with switch disconnected from the wires, and ignition on?
As I remember when taking my transfer box out on an early 90, the difflock switch had one wire going towards the dash, and one wire to ground on the transfercase itself. So that means that the bulb in the binnacle always gets 12V, and it switches on when the switch on the transfer case makes continuity to ground. So the suspect is a chafed wire somewhere between the bulb and the switch.
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I'd say almost certainly that between the lamp and the switch the wire is being earthed, either trapped in something or the insulation has been worn through by contact.
Have you had the dash apart, the tunnel off or the transfer box off ?
Mo
The Land Rover 90 - Many are called, few are chosen.
1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
