Not the usual "Oil Light is on" post

At start up my oil light behaves exactly like it should. On at pos 2 and off the split second the engine starts. Doesn't come on or flicker whilst driving.
Turn the ignition off, walking away, turn round and the oil light is on. It stays on until I start her up again. I've searched the forums and can't see this particular issue. Apologies if it has been asked before and I've just missed it.
I'm assuming that this is just electrical and that I just need to trace a short in the wiring to the light. I'm a novice on electrics. I have a multimeter but not a clue where to start. Could it be the ignition instead of the oil light wiring? Do I just start with the light wiring? Where do I start with the light wiring? Thanks in advance.

I would start by checking the earth for the dash / instruments, most strange electrical problems are due to bad earths.
There shouldn't be any power to the oil pressure light with ignition off and if it was a fault with the key, I would expect the ignition light would stay on as well.

Thanks for the quick reply Rougharse Racing. Would I be right in assuming that the instrument panel earths straight to the bulkhead?

Scrub that question. Just done a bit of research on earth issues in defenders and it's not as simple as that. I'll have a look and see what I find.
Cheers

Pull fuses one by one, see if it goes off, this will help to identify the issue.

Current situation - No oil or battery lights at any time. Battery charges up to 12.4 - 12.5v when no load. Lights on and it drops to 12v pretty quickly. I found that there was no continuity between battery neg post and the transfer case earth. Stripped, cleaned smeared with vasaline now all good. Problem is still the same. Checked the bulk head earth. almost no voltage drop. Checked all the instrument panel earths and all seem good. worst case drop 0.25v. Apart from one that had a drop of 0.9v this was in the block at the back of the lights that includes the oil and battery lights. Ran a temp earth to it. virtually no drop but no difference. I then realised that the wire was black with a white trace so probably isn't an earth. At the alternator B+ terminal I get 12.4v with no load, that is the same earthed to the engine and earthed to the alternator case. With load it drops to 12v. I now think that either my alternator is wired up incorrectly or it is toast (or both). I'll try to post a picture of my alternator. Brown wire to B+ (Top of picture. thin brown with yellow tracer to the post to the right of B+, unmarked but assumed to be D+. white with grey tracer to W. The butchered wire from the black block also to W. Don't know what that is or what it does. Is my wiring wrong and or is my alternator toast or am i missing something with my earth checks? Thanks in advance. Doey

Google A127 alternator, loads of info out there, common as muck, and parts cheap.
Undo them three screws at the bottom with blue paint on, and gently wigggle the brush box out and unplug it, then take a look at the brushes.

lynall said:

Google A127 alternator, loads of info out there, common as muck, and parts cheap.
Undo them three screws at the bottom with blue paint on, and gently wigggle the brush box out and unplug it, then take a look at the brushes.

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It's still under warranty. If the consensus is that the alternator is goosed I'd rather just send it back for a replacement than start taking it apart and voiding the warranty. If my wiring is wrong or it may not be the alternator I'd rather investigate that before send the alternator back.

Complete overhale kit for A 127 about £20

tottot said:

Complete overhale kit for A 127 about £20

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Thanks tottot. I have 2 dead alternators. One under warranty that I'll send back and one on my defender that isn't under warranty that I'll try to overhaul. Both give exactly the same symptoms. Before I put a replacement or overhauled alternator on my defender... is my wiring detailed above correct?

Doey68 said:

Thanks tottot. I have 2 dead alternators. One under warranty that I'll send back and one on my defender that isn't under warranty that I'll try to overhaul. Both give exactly the same symptoms. Before I put a replacement or overhauled alternator on my defender... is my wiring detailed above correct?

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The wiring on the back of that alt pic is wrong.
The w terminal is for the rev counter (if connected) so why it has thta suppresor wired to it I do not know?

Does the charge light work? does the charge bulb work when tested across a battery? does it light up with ign on?
People need much much more info to diagnose stuff remotely.
Pics are way better than words, as people tend to use different words in their own way, so have different meanings to different people.

lynall said:

The wiring on the back of that alt pic is wrong.
The w terminal is for the rev counter (if connected) so why it has thta suppresor wired to it I do not know?

Does the charge light work? does the charge bulb work when tested across a battery? does it light up with ign on?
People need much much more info to diagnose stuff remotely.
Pics are way better than words, as people tend to use different words in their own way, so have different meanings to different people.

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Ahhh. That clears that one up then. I don't have a rev counter. I do have an EGR that needs to sense engine speed. So that is connected to the correct terminal. I didn't know that the black block was a suppressor. I do now. Does the EGR need one or should I just remove it? The bulb was working previously. I can't check it today as it is my wife's birthday and she wants to go to the east coast. I'll let you know. You don't know what you don't know. I can only post about my situation and wait for the questions to come in. As I remember it, that is how conversations work....

EGR are you sure?
What engine is it?
Very very rare on 200
Started to become std fit on 300 1994 onwards
Both dead easy to just blank off

lynall said:

EGR are you sure?
What engine is it?
Very very rare on 200
Started to become std fit on 300 1994 onwards
Both dead easy to just blank off

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She's a 96 300. My wife tells me that my last post was a bit arsey. Apologies, I didn't mean to come across that way. Blanking off the EGR is on my to-do list but is nothing to do with my current situation. Thanks to your input I'm reasonable confident that the wiring is not an issue.
My intention is to get a new alternator whilst waiting for a warranty replacement. Wire it up without fitting and sit it on top of the fitted alternator. Turning the key to ignition without starting I should then have all lights. If not then stop as there is another issue. Is there any flaw in that approach that anyone can see? (other than shelling out for a new alternator to have a replacement on the shelf).

If you have fitted two different alternators, one of them brand new AND the same fault persists, it is pretty safe to say that the alternator isn't the problem.

OP, you have put oil light, do you mean ign light ?

freelance said:

OP, you have put oil light, do you mean ign light ?

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Both. The oil and ignition light should come on before starting the engine. They don't.

the alternator should be if connected wrong the ignition warning lamp is fed straight from battery

mystery said:

the alternator should be if connected wrong the ignition warning lamp is fed straight from battery View attachment 202492

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Thanks Mystery. So if the Ignition / Alternator warning lamp is fed straight from the Battery, regardless of the condition of the alternator, it should light up with the ignition on prior to starting. That means that I still have another issue on top of the issue with the alternator. I'll test the bulbs. I haven't yet checked the earths to the inner wings behind the headlights. I've been focusing on the alternator and the instrument panel wiring. Could they still be an issue? I'll check the bulbs for the warning lights first.

It's been a while but the saga was eventually solved so. I thought that I should post an update so anyone with the same issue can make sure that it isn't the same cause. I didn't find the fault. The fault found me. I was still having the problem of not charging properly, No ignition or oil lights on start up. Oil pressure light started to flicker once warm (I had the pressure checked out and it was fine). Anyway whilst driving on a lane above Hawes we had a small incident. By incident I mean fire. Just a little fire in the wiring harness immediately below injector no. 1. I had nothing to put it out with other than a bottle of water not ideal for an electrical fire but better than letting her burn. The fire also melted the spill return pipe so there was diesel everywhere (at least diesel doesn't burn). we managed to roll down the lane back to tarmac and get recovered by the AA. So at least one of the wires in the harness must have shorted out against the engine or another wire. This eventually got hot enough to ignite the insulation and melt the spill pipe. Here's the result.
It was beyond me to sort it so she had to go in to a local garage for that bit rewiring. All sorted now.

@Doey68

You have to love LR wiring.

Cheers