Originally Posted by
willie
My switch is YUG000540LNF; a latching switch with a headlight symbol and the number 2. I know you can swap the covers around, but the fog light switch is a momentary switch not a latching one.
I can only tell you what worked for me. When I press the switch, with high beam on, I get spotties and an indicator LED.
To get the LED to light up when on, I used it as a negative switch - that is the relay has power, and already has switch provided by High Beam (when on), then with (1) which connected to the earth, so when pressed, the relay is earthed and then functions (relay 'switch' is still the trigger from the high beam). (5) lights up when the spotties are powered on ...
I actually used the link that mello yello posted to work it out, which has this diagram, which explains the inner workings of the switch.
[Posted Image]
I did also go through a lot of fuses, and a switch, by trial and error ... and I managed to blow the LED by indiscriminate application of current .... which caused a bit of frustration until I worked out the LED was never going to light up .... you can probably work out from the diagram where not to hook up power and earth ....
Good luck.
I drew that simplified diagram, showing how the switch works, because I found it easier than trying to explain it
I added it to a wiring diagram, showing how to use it in a Fog Light or Driving/Spot Light circuit, using a standard automotive relay.
The fullsize diagram is on my PhotoBucket page, here -
(click on the thumbnail for a fullsize image in a new browser window)
The relay's trigger feed is shown from the Main Beam (to suit Driving or Spot Lamps), but would be taken from the Sidelights or Dipped Beam circuit (depending on local Vehicle Lighting Regulations) for Fog Lamps.
Don't be fooled into thinking that all of the range of switches in the 2002-> Defender and Discovery II are wired the same, they're not.
You can probably see, from the following pictures, that all the switches start off with a common Brass matrix, which then has holes drilled through it at certain points and links on the sides cut (or not) to change the circuit's route and function of the 5 pins.
I pulled a YUG000540LNF switch apart and took some (bad ) pictures of how it's constructed and how the circuits are achieved.
This picture is of the inside of the switch, which I've annotated to show how the contacts connect accross pins 1 & 4 when in the ON position -
(click on the thumbnails for a fullsize image in a new browser window)
Looking at the circuit inside the switch -
It would be easy to convert this switch to a conventional live switching ON/OFF switch by cutting the brass track between the two holes, as marked in red in this next picture -
By cutting the track at this point, you separate pins 3 & 4
The revised circuit would be as follows -Pin 1 - Incoming Live from Main Beam/Dipped Beam/Side Lights (as applicable)
Pin 2 - Live from Dash Illumination
Pin 3 - Switch Earth (for Green Illumination and Orange 'tell-tale' LEDs)
Pin 4 - Switched Live output to Accessory Relay
Pin 5 - Live in from Pin 4 (to illuminate Orange 'tell-tale' LED)
You could link pins 4 & 5 inside the switch while you had it apart, by soldering a link across the brass tracks but I've just crimped an extra short length of cable into Pin 4 and looped it round into Pin 5 on the connector.
You will still need to use an accessory relay with a switch modified in this way, but at least it will be wired in a conventional manner.
Paul.
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