Fog Lamp Not Working

The fuse is ok, but I'm not getting power to the switch.
I know the lights have to be on, so could it be the headlamp relay? I could do with help from someone who knows there way around a wiring diagram better than me
Where's the ECU on a 1996 fender? There's another box beside the 10AS alarm box behind the instrument binacle, is that it? Or is there a separate ECU box for the fog light?

These may help but not 100% sure that our 96 models use this system as I have a rocker switch rather than 'a switch in the centre of the dash' (from the description). Never had an issue with mine so not looked in to it and cant really comment with any authority. Could be a new thing on 97 model although happy to be proved wrong.

I was going to complain about '96 defender not having an ECU until I saw the wiring diagram, odd term for what I think is just a relay. Although I cannot be sure I would assume it is one of the relays in the fuse box next to the gearstick, although I cannot help you with which, you may need to look at the wring colours.

It used to be relays. If you have hi beam on it cuts the power to the fogs.
Change a relay first.

I assume the relay is the "non-latching switch" mentioned in the documents by @Kwakerman

dag019 said:

I was going to complain about '96 defender not having an ECU until I saw the wiring diagram, odd term for what I think is just a relay. Although I cannot be sure I would assume it is one of the relays in the fuse box next to the gearstick, although I cannot help you with which, you may need to look at the wring colours.

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Trouble is that the Diagram and other info are for a 1997 model whereas we have 1996. I don't have a non latching switch (I have a rocker) and it is by my right knee which is why I think there has been a change.

Kwakerman said:

Trouble is that the Diagram and other info are for a 1997 model whereas we have 1996. I don't have a non latching switch (I have a rocker) and it is by my right knee which is why I think there has been a change.

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Would that not be the same set up as the early ones with the switch on the steering column? Only instead of the being a headlight style switch on the column it is a rocker by the hazards?

dag019 said:

Would that not be the same set up as the early ones with the switch on the steering column? Only instead of the being a headlight style switch on the column it is a rocker by the hazards?

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Probably (assuming the earlier design doesn't use a non-latching switch)

91-96 wiring diragram. Don’t know if this is more help to you. (I knowmit says to ‘95 but that is when the manual was published)

dag019 said:

91-96 wiring diragram. Don’t know if this is more help to you. (I knowmit says to ‘95 but that is when the manual was published)
View attachment 150590 View attachment 150591

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That is more what I was expecting to see, plain old switches and relays

Evening gents. Just in from work and catching up on your suggestions. They're very much appreciated. Kwakerman knows I'm a novice with electrical systems, but I'm keen to learn! The first thing to strike me from what you have all been saying is that my switch (by my right knee) only 'rocks' a bit, to switch the light on. I'm presuming this is a non latching switch? I've never changed it and I've had the Landy for over 12 years, it might have been changed before I bought it though!

Kwakerman said:

These may help but not 100% sure that our 96 models use this system as I have a rocker switch rather than 'a switch in the centre of the dash' (from the description). Never had an issue with mine so not looked in to it and cant really comment with any authority. Could be a new thing on 97 model although happy to be proved wrong.

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I found that picture (in your second screen shot) when I was googling Defender ECU rear Fog Lamp last night. I'm still not sure what it is and have no idea what that arrow is pointing at. Sounds like some sort of relay by the description of it 'waiting to sense the second earth'. Looks potentially tricky to get at behind the instrument binnacle
The headlight relay is involved, but if that was at fault surely the headlights wouldn't work?.

Just taking the dog for a walk and will construct a reply when I get back in.

Kwakerman said:

Just taking the dog for a walk and will construct a reply when I get back in.

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A very important job! Take your time

Right, you had me doubting my sanity but I've been out and had a look / play and photo the user manual (original to the vehicle). Yes it is a rocker switch and not a momentary action., manual says press bottom of switch to turn on, press top to turn off.
1. With the key in the run position and light switch on pressing the rocker switch until it clicks puts the fog light on.
2. Turn light switch off and the fog light goes off, turn it on and the fog light comes on immediately without touching the fog light switch.
3. Same sequence as 2 if you turn the ignition off / on instead of the light switch.
4. With everything turned off (ignition/lights/fog switch) if I then turn the fog light on followed by the ignition and lights then the fog light lights.
All this fiddling around proves that there is no need to reactivate the fog light if the ignition / light switches are turned off then on again.
If you set the fog light switch to On you will see that the rocker is in the same position as the heated rear window switch when turned on (ignore the Hazard switch as this is a different type of switch.
End result is that you don't have a fog light ECU, just a normal rocker switch and a number of relays, nothing clever about it. Doesn't help you at this particular time but stops you going off down a rabbit hole looking for a non existent ECU.
I'll try and have a look to see if I can give you a few pointers, but I wouldn't trust that circuit diagram you have.

Kwakerman said:

View attachment 150624 Right, you had me doubting my sanity but I've been out and had a look / play and photo the user manual (original to the vehicle). Yes it is a rocker switch and not a momentary action., manual says press bottom of switch to turn on, press top to turn off.
1. With the key in the run position and light switch on pressing the rocker switch until it clicks puts the fog light on.
2. Turn light switch off and the fog light goes off, turn it on and the fog light comes on immediately without touching the fog light switch.
3. Same sequence as 2 if you turn the ignition off / on instead of the light switch.
4. With everything turned off (ignition/lights/fog switch) if I then turn the fog light on followed by the ignition and lights then the fog light lights.
All this fiddling around proves that there is no need to reactivate the fog light if the ignition / light switches are turned off then on again.
If you set the fog light switch to On you will see that the rocker is in the same position as the heated rear window switch when turned on (ignore the Hazard switch as this is a different type of switch.
End result is that you don't have a fog light ECU, just a normal rocker switch and a number of relays, nothing clever about it. Doesn't help you at this particular time but stops you going off down a rabbit hole looking for a non existent ECU.
I'll try and have a look to see if I can give you a few pointers, but I wouldn't trust that circuit diagram you have.

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I might have a few things going on here then. My switch must be poorly. I say poorly, because it may not be fully carped. My switch swings back to it's original position when you switch it on. The fog light used to come on when you did this. The illuminated bit has never worked in the switch all the time I've had it. The other thing going on is that I have no power to the switch anyway
I'm going to follow your lead and go and have another look/play with that switch.

Al2O3 said:

I might have a few things going on here then. My switch must be poorly. I say poorly, because it may not be fully carped. My switch swings back to it's original position when you switch it on. The fog light used to come on when you did this. The illuminated bit has never worked in the switch all the time I've had it. The other thing going on is that I have no power to the switch anyway
I'm going to follow your lead and go and have another look/play with that switch.

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Basically my fog and rear demist switches work the same, if your fog one won't latch then that sounds dodgy to start with

I'm a little more confused now.
Here is a picture of my switches

A bit of flash reflection, but the fog lamp switch is permanently in the down position.
When I press it, the fog lamp indicator light illuminates on the dash! I'm uploading a short video to youtube. I'll just be a minute or two.

Here we go

Al2O3 said:

I might have a few things going on here then. My switch must be poorly. I say poorly, because it may not be fully carped. My switch swings back to it's original position when you switch it on. The fog light used to come on when you did this. The illuminated bit has never worked in the switch all the time I've had it. The other thing going on is that I have no power to the switch anyway
I'm going to follow your lead and go and have another look/play with that switch.

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Looks like there are potentially three types of switches, the one touch / momentary ones will be for TD5 or (later with ECU). My VIN is a 'TA' so I have the rocker switch variant, what is your VIN?