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Home > Maintenance & Modifications > Fitting LED driving lights with Xenon HID headlights
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Nodge68



Member Since: 15 Jul 2020
Location: Newquay
Posts: 584

United Kingdom 2008 Freelander 2 TD4 SE Manual Rimini Red

Wyevalley wrote:
A bit more info chaps.

It isn't going to be as easy as I first thought.

I managed to find a 2014 wiring diagram with HID headlights and the shutter motor is fed from a Field Effect Transistor (FET) via pin 10 of the headlight connector (I haven't verified the pin number yet).

The problem is that, doing a bit more research, you can't just tap into that wire and connect to a relay as it has all sorts of odd effects including, so I gather, back emf spikes which could damage the FET when the relay switches off. This can be fixed with a diode but so far I have only found theoretical circuit info, nothing specific to this particular issue so, unless I can find details of a working setup, I will not attempt any experimentation at the moment.

As before, if anyone has succesfully acheived this then details would be gratefully received otherwise I will feedback any info I can find as and when.

Thanks for the comments so far and fingers crossed!



The back EMF from a relay shouldn't hurt a big FET in the headlamp drive circuit. The shutter is already a coil, which will also generate a back EMF, so the FETs are likely protected with a reverse diode.
If you're worried about EMF damage, simply solder a 4001 diode across the relay coil in reverse bias, which will clamp out any EMF, preventing it getting to the FETs. 2009 Rimini Red SE, it's getting there.

Post #418248 7th Feb 2022 8:52 pm
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congoblue



Member Since: 28 Dec 2019
Location: Hull
Posts: 103

United Kingdom 2014 Freelander 2 TD4 SE Manual Loire Blue

What Nodge said, your relay won't damage the FET circuit if you put a diode across it. I'm an electronics engineer in my day job and we run relays off FETs all the time. It basically looks like this (borrowing someone else's diagram)






The FET at the bottom and the resistors are in the car electronics module, switching the negative side of the circuit. You add your relay coil as shown at the top, put a diode across it with the bar to the positive side.

Post #418504 14th Feb 2022 10:16 am
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Wyevalley



Member Since: 25 Jan 2022
Location: Forest of Dean, Gloucestershire
Posts: 13

2014 Freelander 2 SD4 HSE Lux Auto Firenze Red

Apologies for the delay in responding. Life gets in the way sometimes.

Thanks Nodge and congoblue. That seems like a possible answer.

I have identified the two wires going to the shutter inside the headlamp unit and now need to trace these back through the multi pin socket (they are all black wires inside the unit). I have ordered a relay with built in diode so will give it a go and report back.

Just to confirm my understanding, With headlights on dipped beam I should be seeing a permanent positive feed to the shutter coil and the other wire would go roughly 12v negative when I switch to main beam and the shutter should operate. I then wire in my new relay in parallel with the shutter coil with the bar on the diode on the positive side of the new relay coil? Yes?

Thanks.

Post #420839 30th Apr 2022 2:17 pm
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congoblue



Member Since: 28 Dec 2019
Location: Hull
Posts: 103

United Kingdom 2014 Freelander 2 TD4 SE Manual Loire Blue

I think the shutter is activated for full beam and is in its idle position for dipped, but I might be wrong.

When the shutter is inactive you'll see 12V on both wires.
When the shutter is active you'll see 12V on one wire and 0V on the other.

The 0V wire is the one you want. Wire your relay between 12V and this wire.

Post #420842 30th Apr 2022 3:21 pm
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Wyevalley



Member Since: 25 Jan 2022
Location: Forest of Dean, Gloucestershire
Posts: 13

2014 Freelander 2 SD4 HSE Lux Auto Firenze Red

Thanks congoblue. Yes, I believe the shutter operates when main beam is selected so if it fails, it fails on dip beam.

Thanks also for the additional info. It’s been many years since I did any electronic theory at night school!

Post #420846 30th Apr 2022 4:18 pm
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Wyevalley



Member Since: 25 Jan 2022
Location: Forest of Dean, Gloucestershire
Posts: 13

2014 Freelander 2 SD4 HSE Lux Auto Firenze Red

Ok. A bit further along the track and hopefully I can get the final pieces for the jigsaw!

Got old multimeter out this afternoon with the following results (working on the front left hand headlamp) :

The shutter coil is fed by one red wire and one black wire (this may not be relevant).

These connect to two black wires inside the headlamp unit, one of which (the one connected to the red shutter wire) goes to pin 10 of the multi connector and subsequently to a grey/brown wire in the headlamp loom. The other goes to pin 12 of the multi connector and subsequently to a black/yellow cable in the loom. Amazingly this aligns with the wiring diagram I have (the black/yellow being ‘ground’).

Connecting the positive multimeter lead to battery positive the following are the results:

Shutter passive
Grey/brown. 12.15v
Black/yellow. 12.15v

Shutter active
Grey/brown. 0.2v
Black/yellow. 11.79v

Congoblue - your last post advises connecting my new relay (with inbuilt diode) across the 0v wire (grey/brown in this case) and positive.

Can I ask, do my latest investigations confirm this and also could you advise whether this should be a separate (fused) positive feed and which side should the bar on the diode be (pos or neg feed)?

Apologies if I am being a bit dense but I don’t want to mess anything up!

If successful I will put up details of the process in a separate thread as it may be useful to others.

Thanks.

Post #421073 9th May 2022 5:21 pm
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congoblue



Member Since: 28 Dec 2019
Location: Hull
Posts: 103

United Kingdom 2014 Freelander 2 TD4 SE Manual Loire Blue

Yes that sounds correct. So the grey/brown wire is being switched to ground by the control module.

You could just connect the relay across the 2 wires rather than looking for another 12V feed. Diode bar to the permanent 12V wire (so it's reversed - this is to catch the spike the relay coil gives out when power is removed).

Post #421108 10th May 2022 1:39 pm
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Wyevalley



Member Since: 25 Jan 2022
Location: Forest of Dean, Gloucestershire
Posts: 13

2014 Freelander 2 SD4 HSE Lux Auto Firenze Red

Perfect! Thank you congoblue. Can’t get to it for a couple of days but will report progress.

Cheers,

Chris.

Post #421111 10th May 2022 6:39 pm
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Wyevalley



Member Since: 25 Jan 2022
Location: Forest of Dean, Gloucestershire
Posts: 13

2014 Freelander 2 SD4 HSE Lux Auto Firenze Red

Hi All,

I started to have another look at the task this morning and it set me thinking.

When I described the voltage readings i reported earlier I should have perhaps made it clearer.

Because I had the pos lead of the multimeter connected to the pos battery terminal, the voltages I described were negative ones (this is where I perhaps should have made it clearer).

This morning, I connected the neg lead of the multimeter to neg battery terminal (ie. ground) with the headlight connected and got the following :

Shutter passive
Black/Yellow - 0v +
Grey/Brown - 0.02v +

Shutter active
Black/Yellow - 0.04v +
Grey/Brown - 11.6v +

so I believe that the shutter is being switched to (approx) 12v positive when activated. The Black/Yellow remains grounded.

The plan therefore is still to connect the relay across the Grey/Brown and Black/Yellow wires with the bar on the diode connected to the Grey/Brown side.

Does this sound like a plan?

Thanks,

Chris.

Post #421226 14th May 2022 9:27 am
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