Linking headlights to interior light

[geraintthomas]

Just a thought I had.

How easy would it be to wire the headlights to come on when the interior light comes on? A lot of modern cars now have headlights that turn on when you unlock the car, but also when you open the door at night. If the headlights were linked to the interior light, it would give the same effect.

Obviously I'd still like to turn them on as normal, but I just want the courtesy light to turn them on too.

Hard to do?

[JayG]

I imaging with a few relays and the wiring diagram you could .

Might be easier for you to move the steering wheel to the correct side (left)

[geraintthomas]

Well, it was kind of a question towards people who would possibly know how to do it haha.

And I'll keep the steering wheel on the right side thanks very much! (Right in both senses of the word )

[Meir]

that is very interesting mode.
it should be fairly easy to achieve with 1 relay connected at the back of the fuse/relay box.
the only challenge is to locate the correct wires, but they both should be there.
what year is your box?
maybe i can have a look at the diagram for you.

[geraintthomas]

It's a 2003 facelift Boxster S.

Thank you I think it'll be a nice modification. Because modern cars have a feature at night when you open the door the headlights come on, or when you unlock the car it'll come on, etc. Just linking it to come on with the interior light will be all that's needed to do it

[Meir]

Originally Posted by geraintthomas

It's a 2003 facelift Boxster S.

Thank you I think it'll be a nice modification. Because modern cars have a feature at night when you open the door the headlights come on, or when you unlock the car it'll come on, etc. Just linking it to come on with the interior light will be all that's needed to do it

Yes I totally get it.
I might even do it on my 02 996. Should be same electrical system.
What did you had in mind? Activate the parking lights, or the main?

[thstone]

This should be fairly easy.

The headlights are powered from a relay that is activated by the switch. All you have to do is activate the relay. One way to do this would be to tap into one of the wires powering the interior lights and run it to the correct pins on the headlight relay. Thus, when the interior lights turn on, the headlight relay will be switched on and then the highlights should turn on.

This is very similar to the hack that I posted to control the engine compartment fan using a manual switch (Engine Compartment Fan Manual Switch).

What I'd have to check is what type of relay the headlights use (standard Type 53 or something else) to figure out which pins to jumper and if the 2003 S is wired close to the same as the 97-99 base that I have - but the principle should be the same even if the exact details are different.

[stelan]

But your wife will notice when you sneak out at night and that is a big no, or is int?

[particlewave]

Originally Posted by thstone

What I'd have to check is what type of relay the headlights use

None.

A switch and some fuses is all (this is why our switches are so prone to failure).

[geraintthomas]

I know there's a hack to turn the fog lights on with the car by using a jumper between fuses. Maybe a similar approach?

[geraintthomas]

Originally Posted by particlewave

None.

A switch and some fuses is all (this is why our switches are so prone to failure).

I would have thought if there's anyone here that could do it, it would have been you any idea on how this could be done?

[Meir]

Pwave is right.
I spent couple of hours last night, going over the diagrams looking for the headlights relay that doesn't exist
But just
I will post some diagram later on how I think it should be done, but basically you need to use a relay to jumper between the red and white/black wires, at the light switch.
Both are heavy gauge, so you will need a 30/40 amp relay.
The relay will be activated by the brown/yellow wire that comes from the BCM.
Since it is running all over the car, it can probebly be located at the ckick panel/ fuse box area. Same goes for the wire that comes from the light switch. It goes into the fuse box, and comes on the other side as yellow/black.
Obviusely you need to connect before the fuse.

[geraintthomas]

Originally Posted by Meir

Pwave is right.
I spent couple of hours last night, going over the diagrams looking for the headlights relay that doesn't exist
But just
I will post some diagram later on how I think it should be done, but basically you need to use a relay to jumper between the red and white/black wires, at the light switch.
Both are heavy gauge, so you will need a 30/40 amp relay.
The relay will be activated by the brown/yellow wire that comes from the BCM.
Since it is running all over the car, it can probebly be located at the ckick panel/ fuse box area. Same goes for the wire that comes from the light switch. It goes into the fuse box, and comes on the other side as yellow/black.
Obviusely you need to connect before the fuse.

Thank you

My only concern is that I use HID's, and the courtesy light uses a dimming feature to turn itself off. I wonder how that would affect the HID's - I'm hoping they'd just turn off once the voltage goes under a certain amount.

[Meir]

Originally Posted by geraintthomas

Thank you

My only concern is that I use HID's, and the courtesy light uses a dimming feature to turn itself off. I wonder how that would affect the HID's - I'm hoping they'd just turn off once the voltage goes under a certain amount.

well, the courtesy light will not be connected to the low beam circuit.
it will activate a relay that will switch the lights on and off.
so when the courtesy light will dim out to a certain level (in voltage), the relay will interrupt the lights circuit instantly.
the relay i tested disconnects/reconnects at 3-5 volts range.
here is a quick video i made.
https://youtu.be/mOkvLh2l1fw
pay attantion to the clicking noise coming from the relay, once the lights dimm out at around 3-5 volts
ignor the first click sound that is coming from the power supply.

[jb92563]

Just a related thought:

A 55w headlight draws about 4.5 amps each so without a relay, upgrading to a higher watt headlight bulb as some folks do will also shorten the life of the light switch (as well as burning the plastic lens).

You will need to put in a 10amp+ relay for the headlights that will now trigger from the light switch AND the courtesy light signal wire?

Wondering if the current will flow the wrong way and damage something if the signals are not isolated from each other?
Perhaps a couple diodes will prevent that possibility?

[Meir]

Originally Posted by jb92563

Just a related thought:

A 55w headlight draws about 4.5 amps each so without a relay, upgrading to a higher watt headlight bulb as some folks do will also shorten the life of the light switch (as well as burning the plastic lens).

You will need to put in a 10amp+ relay for the headlights that will now trigger from the light switch AND the courtesy light signal wire?

Wondering if the current will flow the wrong way and damage something if the signals are not isolated from each other?
Perhaps a couple diodes will prevent that possibility?

it will be no problem.
the added relay will act as the switch itself. no need to isolate anything, as the relay will imitate the switch.
you are right about the load though, that is way the switch is so robust and more have duty (compared to other cars that uses a light relay)and uses thicker wires. not that it really helps as mentioned by Pwave.
i have to admit i was surprize to find out that the light system do not incorporate a relay.
circuit diagram to follow in a bit.

[Meir]

the diagram for the light system is scattered over few pages, so i had to build a small puzzle. i also apologize for the low quality pictures taken with my cellphone.

first, this is where you can see the main power line (red wire) going into the switch.



if you follow the line to another page, you can see it goes to the current distributor.



the current distributor is basically a junction box from the battery positive lead, backed up by 80 amp fuses. it's located behind the ac air box.

now, this is the line that comes out of the switch (white/black), splits in two, goes to the fuse box, and on the other end, change colors and go to each individual head light.




on the other side of the fuse box the colors changes to yellow/black for the left headlight, and yellow for the right.

[Meir]

and here is the relay diagram.
obviously, the easy way is to locate the relay next to the light switch, and run a wire to the A pillar/cick panal to get to the courtesy light wire.
i will try and have a look this weekend and see where the best place to connect.

[geraintthomas]

This is looking VERY promising! Be sure to write a guide!

[particlewave]

If your courtesy lights dim out, you'd need a controller circuit to power the relay. Otherwise, the relay would chatter as the voltage drops to near the relay solenoids threshold. This would cause premature failure of said relay and wreak havoc on the HID ballasts and bulbs.
You'd need a micro controller that applies/cuts power to the relay at a predetermined threshold.

Even with the controller, they'd want to come on and off a lot and would not be good for the HIDs. Incandescent fog or parking lights would be better.