[DML] DIY "Headlights Off When The Car Is Off" mod
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[DML] DIY "Headlights Off When The Car Is Off" mod

I kept forgetting to turn my headlights off when I got out of the  
car, since there's no buzzer or anything to warn you about it, so I  
added a relay to the headlight switch to do it for me when the  
ignition is off.  I just leave my lights on all the time now, even  
during the day.  I did this a couple of years ago, well before DMCH's  
reproduction headlight switch with its built-in auto-off feature was  

- Pre-wired relay socket
- Relay
- Method to connect the relay to headlight switch wiring, which could  
-- Male and female blade-style connectors and a crimp tool
-- Butt connectors and a crimp tool
- Optional:  Inline fuse holder and fuse


- DeLorean Parts NW's Headlight Switch Safety Bypass Kit, which uses  
all the same parts and doesn't require a crimp tool.  It's only $10,  
and has everything you need.

I also really like the Power Probe, which is a simple electrical test  
tool for automotive work.  Once connected to the car's battery, you  
can touch any electrical connection and tell if it is positive or  
negative via an LED an optional buzzer.  Furthermore, you can test  
circuits (and, if you're reckless, blow fuses) by applying positive  
and negative via a switch on the probe.  I have a Power Probe II  
(there are also I and III).  It's very handy for finding, say,  
ignition-switched wires, or seeing if a circuit has power, or making  
sure a circuit works when you apply 12v or ground to it, and so on.   
Google Product Search has the I for about $50, and the II for about  
$90, and the III for around $100-$180.  If you plan on doing a lot of  
electrical work, I recommend it; if you're just doing one or two  
things, you can just get away with a multimeter.


I've also taken to using a label printer to thoroughly document any  
new wires I add to the car, so that I'll know what the heck I did  
when I look at it in the future.  I got a portable Brother label  
printer, and it works great.

   Relays and Sockets:
You can get the relays and sockets from various sources.  They  
usually come with wires already attached.  Any standard automotive  
relay will do.  Google has lists a bunch of both, and I'm sure you  
can find all of these parts locally easily enough.

   Accessing the Headlight Switch Wiring:
I chose to do this from the headlight switch.  You can probably do it  
from the fuse box behind the passenger's seat, but I knew that  
everything went through that switch and decided that was the route I  
would take.

There are two ways to get access to the back of the headlight  
switch.  I did the method that didn't require taking apart the center  
console, which involves reaching behind the console from the driver's  
side and unplugging the connector from the headlight switch.  This is  
pretty annoying to do and you cant see what you're doing, and it's a  
bit of a pain to reconnect the switch to the plug, but it's not too  
horribly bad.

The second method is to remove the headlight switch itself.  I  
recently installed DeLorean Parts NW's headlight switch safety  
bypass, and his instructions work well in this situation as well.   
First you remove the three climate control knobs, and then the long  
screw behind the center knob.  You can then pull out the face plate  
and wiggle the headlight switch out of its socket, pulling the wiring  
through with it.  I'd suggest getting the safety bypass and doing  
both installations at the same time.

The third method might be easier if you already have an after market  
radio, and is what I did while I was also replacing the rubber  
cowling on my center air vents and installing the above headlight  
switch safety bypass.  I've removed my radio so many times that it is  
mostly held in by pressure from the metal mounting cage rather than  
those bent metal clips, so it's easy for me to remove.  I used two  
coat hangers bent 90 degrees at the end to release the clips that  
secure my Sony stereo to the cage so I could pull it out and unplug  
it.  I also removed the metal frame that holds the stereo in place,  
which gave me excellent access to the headlight switch wiring.  This  
might be a lot of work for some people, and I have no idea what's  
involved with the stock radio, so you might just want to go with the  
first or second methods instead.

Installation is fairly straight-forward.  As usual, you'll probably  
want to disconnect the battery before you proceed, just in case.   
After that, you need to insert a relay between the headlights and  
switch.  I used butt connectors, but you can do whatever you're  
comfortable with.  I was rather impressed with the quality and ease  
of installation of DeLorean Parts NW's headlight switch safety bypass  
kit, so if you want to keep it simple you can just buy another one of  

If you do use DMC Parts NW's kit, you would do the following:

First, pull the headlight switch's connector out far enough that you  
can get to the wiring.

1 - The Blue/Brown wire actually powers the headlights, and it is  
this that the relay will switch.  Install two T-taps about an inch  
apart on the Blue/Brown wire, then cut the wire between the T-taps.

2 - Connect the relay socket's Blue wire to one of the T-taps on the  
Blue/Brown wire.

3 - Connect the relay socket's Yellow wire to the other T-tap on the  
Blue/Brown wire.

4 - Install a T-tap on the Black wire on the headlight connector.  We  
use this to provide ground to our relay.

5 - Connect the relay socket's White wire to the T-tap on the Black  

6 - Locate an "accessory" wire.  This is a wire that is hot only when  
the key is in the "run" position.  I actually ran a wire from the  
relay/fuse compartment from behind the passenger seat to the number  
#35 relay ("Aux Relay -- Accessory Position -- 1") in the fuse and  
relay diagram in the Workshop Manual section M:07:02.  You're looking  
for a wire that is reads positive only when the key is in the "run"  
state; you should be able to easily find this via a multimeter.  It  
is very likely that there is such a wire under the dash, but I'm not  
sure where at the moment.

7 - Connect a T-tap to the "accessory" wire.  This will turn energize  
the relay when the key is set to "run".

8 - Attach the relay socket's Black wire to the the T-tap on the  
"accessory" wire.

9 - Put a relay into the relay socket.

The middle wire on the relay socket is unused in this application,  
and has been removed on DMC Parts NW's kit.

I recommend keeping the relay socket's wires at their full length.   
You can then stuff the relay and socket through the headlight  
switch's hole and get it out of the way so it doesn't interfere with  
anything else.  I pushed mine toward the back of the car and down to  
the left towards the driver's side.  You can probably reach around  
the back of the center console from the left side and pull it through  
enough that it's out of the way.

Be careful not to block the temperature knob with the relay.  At  
first, I inadvertently jammed the temp knob by placing the relay to  
the left of it, thus blocking the arm from moving to the left and  
keeping me from turning the heat up beyond the middle setting.  You  
might want to turn that knob all the way to "hot" before positioning  
the relay, and making sure that the knob still has its full range  
before putting everything back together.

You can optionally install an inline fuse in this setup.  I put one  
between the relay's Black wire and the
"accessory" between steps 7 and 8.

   Testing and Operation:
That's it for the wiring.  To make sure it works, plug the headlight  
switch back into the socket, set it to the "off" state, and reconnect  
the battery.

Since the car is off and the headlight switch is off, the headlights  
should also be off.  Push the headlight switch through the parking  
light position, the "on" position, and back to the "off" position;  
the headlights should remain off the entire time.

Now put the key in the ignition and turn it to the "run" position  
(you don't need to start the car).  Since the headlight switch is  
off, the headlights should also be off.  Push the button once and  
make sure the marker lights are on.  Push it a second time and make  
sure the headlights are on.

If you turn the car off now, the headlights should also go off.  If  
you start the car, the headlights should turn off while the car is  
cranking, and come back on when the key returns to the "run" position.

You can now leave the headlight switch in the "on" position all the  
time, and never have to worry about forgetting to turn your  
headlights off again.

   Re-Assembling the Center Console:
To put the console back together, you simply need to snap the  
headlight switch back into place, put back on the face plate, replace  
the screw near the center knob, and put the knobs back on their  
respective switches.

The total cost of this project is under $10, if you get everything  
locally or already have the parts lying around, and $10+shipping if  
you just repurpose the DeLorean Parts NW Headlight Bypass Kit.  I've  
run with this for a few years now and never had any problems, and I  
don't have to worry about forgetting to turn off my lights anymore.

-- Joe

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