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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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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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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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that went way over my head Sloth... do you have a photo or diagram pls?

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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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Thanks - doesn't sound too tricky then, I'll give it a bash

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Since I had my dash off, as I put things together I thought I'd give this a crack. But I've ended up with headlights (no side lights) flashing at ignition off (and HL switch on) !!

Easy enough to roll back if I can't solve it, but what I changed was pretty trivial:
i I depinned C219/3 Black (ground to E252) which goes to the Headlight (H/L) switch
ii I replaced it with a new pin/ earth wire going to a 4 pin relay
iii I put the other side of the 4 pin relay to the earth at C619/ Cigar lighter (which grounds to E621)
iv. to activate the relay I used the +ve and -ve of C619/ Cigar lighter

I can feel the relay come on with ignition on, and go off with ignition off. With ignition on, the switch functions fine. With ignition off and H/L switch on then the headlights and tail lamps (but not sidelights) flash as well as the interior lights (HVAC display, clock, dash), even if I remove the relay from its base.

Is it possible that the BeCM (mis) interprets the lack of earth at the H/L switch (ie when ignition is off) and then starts pulsing the headlights. The flashing command can presumably only come from the BeCM?

I'll think some more...anyone else got any genius ideas?

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I can disconnect everything at C619 and the car still does the flashing thing. The only thing I haven't done yet is take the new pin out of C219. The new pin I used (econoseal) was microscopically different from the original one, I'm just wondering if it's not delivering a good connection - but then how would the switch be functioning fine at ignition on, if it had a poor earth connection?
Is there a document somewhere which lists off the connector make & type of each connector?

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I think the pin type is a red herring (still interested for the future, if some has a reference doc for Connector make/ model).
If I put the lights on with ignition on and remove the relay I get the same flashing effect so the new pin seems fine - but the second you remove the earth from the H/L switch - either because the relay is inactive, or the relay has been removed then you get the flashing (the lights don't do anything with switch off). I'm assuming it is some sort of BeCM logic I have fallen foul of - so maybe it's just better not to try and interrupt the ground to that switch.

Any thoughts? I may just replace the original ground pin in C219 and see what happens if I put the relay on the OR wire to interrupt the headlight wire to the BeCM instead

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Disconnecting the ground from pin 3 of C219 is no different to the headlight switch being in the off position, no ground signal being sent to the BeCM. I was wondering if you'd wired the relay wrong so the BeCM was seeing the ground through the 300 or so Ohm resistance of the relay coil, but if that was the case, then all that would happen would be that the lights wouldn't operate at all with the relay removed (and it probably wouldn't operate with the ignition on). Check that the relay is wired correctly, ignition switched power to pin 85, ground to pin 86, and use pins 30 and 87 to break the ground to the headlight switch.

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Does it matter which way round 85 and 86 were with a std relay? My bench test said no. (9V battery across the coil and measuring resistance across 30/87). I actually have 85 going to ignition anyway, so that's ok.

"Disconnecting the ground from pin 3 of C219 is no different to the headlight switch being in the off position, no ground signal being sent to the BeCM" - i thought the same - but really it's not as the ground wire is still attached to the switch - perhaps "the system" needs that ground whether or not the switch is on.

Anyway - i've replaced the original ground on the H/L switch and reconfigured my relay wiring to break the U/Blue wire instead. And then if that works/ I can be bothered I'll put a second relay on the OR to do the side lights

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I just put the relay between U/ Blue and the H/L switch and it works no problem (still driving the coil of the relay from the cigar lighter). Like that it still leaves the ability to have Park lights on, so I may just leave things there, as I guess that function is of some use. The relay will end up in the centre console cubby, so it can easily be replaced, or just jumped, without pulling things apart

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romanrob wrote:

Does it matter which way round 85 and 86 were with a std relay?

It may if the relay has a built in diode to prevent the back emf from damaging whatever is driving it. It's very weird what you've found as disconnecting the ground shouldn't have any other affect. It is there to give a path to ground from the switch illumination and on one side of the two switches so why it didn't work I have no idea.