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Joined: Apr 23 2019
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Simple enough request...lots of folks seem to have searched for the programmable solution, and failed in the past. So what's the most elegant way to achieve this? I. Insert a relay on the headlight position of the rotary switch for the lights ( and tie the relay across an ignition dpdt wire, such as the stereo's position II live), or II. Change the +ve power source for the head lights in the fuse box from a perm one to an ignition dependent, or some other....
I had a self inflicted flat battery this weekend ( ie left the lights on) and want to eliminate the risk of that again...I'm sure someone smarter than me's already cracked it

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Joined: Dec 30 2015
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Do the lights stay on after the ignition is switched off? I know if you turn the ignition off first and then teh lights you get the headlight delay so you can find your front door but I always thought the lights would time out if you left them on. So I've just been outside and switched mine on without the ignition and, yes, they do come on and don't appear to turn off. You could fit a relay but don't forget that the switch doesn't switch power to the lights but applies a ground to the BeCM which supplies power to the lights. Or use your Nano to turn on Daylight Running Lamps then they will come on, and go off, as soon as the engine is started......

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Joined: Jul 12 2016
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Gilbertd wrote:

Do the lights stay on after the ignition is switched off? I know if you turn the ignition off first and then teh lights you get the headlight delay so you can find your front door but I always thought the lights would time out if you left them on.

Mine turn off after a little while. I've not timed it but it's quite a long time. Long enough for people warn me I've left lights on when I get out.

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I have a china china automatic headlight box fitted to mine, which is powered by the accessory circuit (did this by design- so the box loses power during cranking and the lights go off).

All it does really is control a relay that grounds the dipped beam on position. So I retain control over the switch and can leave the lights on if I want, but they are also automatically controlled (and using a spare combination of fog lamp switch cover and latching dash switch in the empty spot, I can disable the automaticness too).

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Joined: Apr 23 2019
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that went way over my head Sloth... do you have a photo or diagram pls?

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Joined: Apr 23 2019
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That's a good point, GD. The switch has a common earth for the side/ head an interior lamps, so probably not the solution. From the ETM doesn't seem like there's a single fused supply for just the headlights either, and by the time the BECM distributes the power to the lights it's going left/right down 3/4 wires per side. So maybe I have to leave this task for when I have to refurb the BECM and jump the tracks :o) Unless Sloth can tell me what this china china magic box is !!

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No there's no fused supply to the headlights, in fact there's no fuses at all, it's all done by the MOSFETS in the BeCM. They supply the power and are overload protected so if there is a short to ground that would ordinarily blow a fuse, the MOSFET shuts down and turns the supply off to that circuit until the short is removed. Sloth's china china box, which I think should probably have read cheapo china box, is a box to switch the lights on automatically when it gets dark and will switch them on (by applying a ground to the main switch) even when the switch is in the OFF position. As it is powered from the Accessory feed from the ignition switch they will go off, assuming it is dark enough for it to have switched them on, as soon as the ignition is switched off. However, it won't affect the operation of the light switch so if you've switched them on, they will still stay on.

I toyed with the idea of doing something similar but using the output from the sun sensor that is on the top of the dash for the HEVAC but it only really detects sunlight so it would have turned the lights unless there was bright sunshine hitting it. In the UK for most of the time I may as well have just turned Daylight running light on......

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Sorry, what Richard has said explains what mine does nicely :)

If you're not bothered about being able to turn the lights on with the ignition off etc, and want to retain using the switch, what you could do is put a relay in line with the ground wire to the switch. That way, you can put the switch to either sidelights, dipped beam or off, and it will work as normal, so long as the ignition etc is on. When you turn the car off, the relay goes off and thus the ground to the switch is interrupted, and the lights go off without you having to think about it. At the same time, if you don't want them on, you can turn them off with the switch as normal. You just wouldn't be able to turn them on without the ignition or accessory position turned on.

As mentioned earlier, the lights can be programmed as 'daytime running lights' to include the tail lights and dipped beam so they'd be on all the time. I don't know if the dash lighting is included in that though - so at night you'd still have to turn the switch on to light the dash up, and then when you turned the car off, the headlights would stay on... defeating the point somewhat. Plus, you wouldn't be able to turn them off if you actually wanted them off without reprogramming the options.

China china, cheapo china, is there a difference? :)

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Joined: Apr 23 2019
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Thanks Sloth/ GD. I thought china china was some clever sort of switch I hadn't come across.

I still don't speak ETM fluently, but it looks the interior lights, or some thing to do with them, are also getting their ground through that rotary light switch. Do you know how relevant that is? Also, how good an earth does the connection need? Presumably the MOSFETs have their own ground, and the switch going to ground is just a signal ( or not?) . If possible I want to try and avoid burying a relay behind the switch panel,so wd probably locate it under the dash somewhere, hence the circuit might need to be a bit longer than it is currenly

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The switching of the lights in the dash, goes to the logic board of the BECM - to trigger it and tell it the switch is turned on. It then internally triggers the appropriate MOSFETs for the lamps that have been turned on side/tail lights, dipped beam,main beam etc.

As Sloth mentions, the easiest way to disable lights is to put a relay in the common ground feed to the sidelight switch, so that when ignition is off, lights get cut automatically.

The MOSFETs in the BECM are grounded internally in the BECM. The headlamp units themselves are grounded in the engine bay.

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Joined: Apr 23 2019
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Thanks - doesn't sound too tricky then, I'll give it a bash