Tail lights on with DRL's

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jtonline
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Tail lights on with DRL's

Post by jtonline » Fri Jul 31, 2020 8:26 pm

I've just bought some bits with the aim of wiring the tail lights so that they come on with the ignition without the side lights switch being on. Then they'll be on when the daytime running lights at the front are.

If all goes according to plan, I'll post how I did it, if anyone's interested. There is no doubt more than one way to achieve this, and I'm not an auto electrician, but what I have in mind should work. I may get an opportunity to make a start tomorrow.

relays.jpg

Julian.
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HouseSpider
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Re: Tail lights on with DRL's

Post by HouseSpider » Fri Jul 31, 2020 8:58 pm

I'm probably wrong, but I thought that Mazda could configure the rears to come on automatically with the drls just by reprogramming. I'm sure it's mandatory to have such in some countries. So if Mazda sells there, then is it done using software or additional hardware?
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Re: Tail lights on with DRL's

Post by jtonline » Fri Jul 31, 2020 9:38 pm

Yeah, I did think of that, but I'm not sure Mazda UK would give the necessary info. to my dealer for them to do it, and then there's the labour cost.
For me to do it myself programatically, (if indeed it's possible) I'd have to obtain the codes to change in the BCM (and I couldn't find any on t'interweb) plus buy a modified ELM327 OBD2 programmer.
The way I'm proposing has only cost me £10.14 and is just a fun little project ;)
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santa
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Re: Tail lights on with DRL's

Post by santa » Sat Aug 01, 2020 5:55 am

It's not possible to programme it on Mazdas, so I had my dealer install a small relay when I bought my car.
I imagine they've done something similar to what jtonline are doing.
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HouseSpider
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Re: Tail lights on with DRL's

Post by HouseSpider » Sat Aug 01, 2020 5:15 pm

👍
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Re: Tail lights on with DRL's

Post by Strangways » Sat Aug 01, 2020 6:17 pm

I find this all very confusing. I understand the front daytime running lamps, that's not a problem. I don't understand, why you, or the driver who is potentially going to drive into the back of you, haven't turned their lights on, because it is obviously too dark to see where you are going. None of this makes any sense at all. This guy behind you must be driving at around 100 mph in the dark to catch up with you at such a speed that he is likely to run into you. You, of course, are also driving in the dark without your lights on. How do you see where you are going?
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AndyRen
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Re: Tail lights on with DRL's

Post by AndyRen » Sun Aug 02, 2020 11:00 am

Will you not get a back feed from the rear tail lights to the front side lights once you've supplied power to them? Or are you installing diodes in the original power feed? Depending on how they're originally wired of course. Just a thought....
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jtonline
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Re: Tail lights on with DRL's

Post by jtonline » Sun Aug 02, 2020 9:17 pm

Thanks for your comments.
Back feed to the sidelights should not be a problem because of the way I'm using the relays.
I've installed two changeover relays behind the plastic boot trim (one on each side) connected to the tail light wiring loom connector.
The relays I've chosen have a built-in flyback diode across the coil terminals 85 & 86 to eliminate any voltage spikes when de-energised.
I've cut the 12v feed wire from the sidelight switch and connected the switch side to relay terminal 85 and normally open terminal 87 and the light side to common terminal 30.
The normally closed relay terminal 87a will be connected to 12v from the fuse box when the ignition is on.
Relay terminal 86 is connected to ground wire on the tail light.

Therefore, when the ignition is on the tail lights will be on. Whenever the light switch (or Auto) is turned on, the relay coil will be energised and the contact will changeover to connecting the light switch 12v feed to the tail light instead of the ignition 12v.

The only thing I haven't done yet is run the wire from the relays to the fuse box, because I ran out of time yesterday, so it's not fully working as intended yet.

changeover-relay.jpg

Julian.
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st3v3cx-3
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Re: Tail lights on with DRL's

Post by st3v3cx-3 » Mon Aug 03, 2020 1:33 pm

Have you sussed out how to achieve the following for your change to the wiring for the tail lights? :D ;)

"Yes, the Daytime Running Lights (DRL's) go off when the handbrake is applied, and also when an auto gearbox is put into Park."
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AndyRen
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Re: Tail lights on with DRL's

Post by AndyRen » Mon Aug 03, 2020 3:59 pm

st3v3cx-3 wrote:
Mon Aug 03, 2020 1:33 pm
Have you sussed out how to achieve the following for your change to the wiring for the tail lights? :D ;)

"Yes, the Daytime Running Lights (DRL's) go off when the handbrake is applied, and also when an auto gearbox is put into Park."
Was just about to ask the same question! 8-)
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