Discovery 2 heated windscreen

Hi all, just a quickie is the rear heated switch the same plug configuration as the front just a different picture on the front.

tomanytoysuk said:

Hi all, just a quickie is the rear heated switch the same plug configuration as the front just a different picture on the front.

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Internally, both switches are wired the same -

Pin 1 - From BCU

Pin 2 - Dash illumination live

Pin 3 - Not used

Pin 4 - Earth

Pin 5 - Warning light live from BCU


They both work by making a momentary path to earth (from Pin 1 to Pin 4), which the BCU detects and switches-on the requested screen.

While the screen is 'on', the BCU also provides a live to Pin 5 to light the switch warning light.

If climate control is fitted, pressing the 'defrost' button also instructs the BCU to switch on the front and rear screens.


The heated rear window switch uses a Black switch connector.

The heated front screen switch uses a Green switch connector.

These connectors are not interchangeable, unless you pare-off the keyways on the connector.

If you want to change the connector shell for the correct one, I sell them on eBay (see link in signature).

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Big thanks paul

Hi just one more question ,can I take feed wire going to the rear switch ,splice into into it and put the feed into the front heated window switch or will this be to much for the BCM.

tomanytoysuk said:

Hi just one more question ,can I take feed wire going to the rear switch ,splice into into it and put the feed into the front heated window switch or will this be to much for the BCM.

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The wires used by the BCU to detect the front or rear window switches being pressed, come from different terminals on the BCU's connectors.

What is it that you're trying to do?

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tomanytoysuk said:

Hi just one more question ,can I take feed wire going to the rear switch ,splice into into it and put the feed into the front heated window switch or will this be to much for the BCM.

Click to expand...

have you got a front screen switch?

like wise! what is it you are trying to do?

i have just put heated screen into mine , got new switch from landrover,

Hi . I have got a rear heated window switch in place of the front one, next week I'm having the front windscreen replaced with a heated one , what I'm trying to get round is going to land rover for them to activate the BCM , just trying to find a cheaper option.

tomanytoysuk said:

Hi . I have got a rear heated window switch in place of the front one, next week I'm having the front windscreen replaced with a heated one , what I'm trying to get round is going to land rover for them to activate the BCM , just trying to find a cheaper option.

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If you can find someone near you with a Nanocom or Hawkeye, I'm sure that they would enable the heated windscreen for a couple of :beer2:

www.discovery2.co.uk/ Nanocom Locator, get help from your Land Rover Buddies!!!

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tomanytoysuk said:

Hi . I have got a rear heated window switch in place of the front one, next week I'm having the front windscreen replaced with a heated one , what I'm trying to get round is going to land rover for them to activate the BCM , just trying to find a cheaper option.

Click to expand...

like paul says,

you still need a nancom or hawkeye to activate it,

Hi I have a problem with my front windscreen demister not working. It''s a D2 2001 that has a heated front windscreen factory fitted. When I press the dash button nothing happens, no light, no relay click. I have just replaced the missing relay with the correct part. Both fuses f7 and f8 are fine. Here is what I have found:
I have 14v at the relay on 2 of the 4 pins.
I have 0v at the purple wire at the switch
I have 0v at the screen connector in the rain gutter

I haven't tested the timer unit because I don't know where to find it. Having power at 2 of the relay connections tells me that the relay is getting power and should activate, and logic says that the switch has operated the circuit. Any suggestions anyone?
Thanks, Chris

The dash switch is a non-latching momentary switch, which switches a wire from the BCU to earth.

This signals the BCU to switch the heated windscreen relay's coil to earth, which it does for the timed period.

During the timed period, the BCU supplies a live to pin 5 of the dash switch, in order to illuminate the switch's tell-tale LED.

Check that the dash switch's earth, on pin 4, is OK - if the switch's night-time illumination works with sidelights switched on - then, the earth is OK.

You will also need to check that the BCU has the heated windscreen option enabled - you'll need an appropriate tool to do this - Nanocom, Hawkeye, etc...

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Thanks Paul, I'm pretty sure the night illumination works. I will try to get a diagnostic tool on it. I can't imagine why the screen would be switched off but it's worth checking. Do you know where the timer unit is situated in case this is faulty? I unscrewed the dash fuse box today in case it's behind it but couldn't see the grey unit I've seen pics of online. Incidentally the rear demister works OK. Is this on the same timer or does it use a separate unit?

The timing function is performed by the BCU

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Just a quick one, its kind of in the same ball park. Could you theoretically remove the rear windscreen cables and use them to power an led light. Electrics is not my strong point but am I right in assuming that one cable is + and one is - and so I could just plug it straight in?

Maxwell85 said:

Just a quick one, its kind of in the same ball park. Could you theoretically remove the rear windscreen cables and use them to power an led light. Electrics is not my strong point but am I right in assuming that one cable is + and one is - and so I could just plug it straight in?

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You could. However the power will only be there when the engine is running, and has a timer of about 10 minutes or so. Why not just run more wires, with a separate switch?

Maxwell85 said:

Electrics is not my strong point but am I right in assuming that one cable is + and one is - and so I could just plug it straight in?

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In that case I suggest that U get someone who is. Be safe

Maxwell85 said:

....Could you theoretically remove the rear windscreen cables and use them to power an led light.....

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what's that ? ...rear windscreen

sierrafery said:

what's that ? ...rear windscreen

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The glass bit in the tailgate door.

It means i missread this thread's title then

cmryan said:

Hi I have a problem with my front windscreen demister not working. It''s a D2 2001 that has a heated front windscreen factory fitted. When I press the dash button nothing happens, no light, no relay click. I have just replaced the missing relay with the correct part. Both fuses f7 and f8 are fine. Here is what I have found:
I have 14v at the relay on 2 of the 4 pins.
I have 0v at the purple wire at the switch
I have 0v at the screen connector in the rain gutter

I haven't tested the timer unit because I don't know where to find it. Having power at 2 of the relay connections tells me that the relay is getting power and should activate, and logic says that the switch has operated the circuit. Any suggestions anyone?
Thanks, Chris

Click to expand...

I'm about to put a heated windscreen in my Discovery 2, I've got the switch and Relay.

Where does the relay need to go?