Ignition Switched Headlights

[codekiddie]

Maybe it's my age, but it seems that my better half is having to remind me more and more, to switch off the lights on the Rover when I park in the garage :shock: I do like the feature on moderns whereby the headlights switch off with the ignition, so I decided to add the same feature to the Rover. This modification only switches off the headlights, allowing for the sidelights to be kept on, as may be necessary :shock:

As with all other jobs electric, the first thing I do is disconnect the battery, (using the quick-disconnect I have installed)

This is a fairly simple task consisting of one relay and base, one fuse and fuse-holder, and a few bits of wire and connectors.

Luckily I have a spare switch assembly, which made it easier to decide where to mount the relay/fuse assembly and take pictures

On the Rover there is a connection between the light switch and the dipped/main switch, (circled in the picture above). It is this connection that will now be switched by the relay, and the relay simply energised when the ignition is on.

The relay base and fuse-holder handily interlock with each other.

The position of the relay/fuse-holder assembly was chosen for its easy access to a ground connection and the light switch.

A piggy-back connector was used for the ground connection for the relay coil, for ease of connecting into the existing wiring.

The other end of the ground connection.

The relay coil wiring finished. The incoming white wire, (the same colour as other ignition switched wires in the car), is the ignition switched +12V, which goes to one side of the fuse. The other side of the fuse connects to one side of the relay coil, and the other side of the coil to ground. When the ignition is switched on, the relay will also switch on.

Showing how the piggy-back ground connection fits together.

On my spare switch unit I used the same cable that is in the car to make the lead to connect the light switch to one side of the relay contacts. The other side of the relay contacts will go to the corresponding wire in the car, once it has been removed from the light switch.

Showing the cable in place from light switch to relay contact.

The top hole is where the cable in the car will go, (the other side of the relay contacts).

Behind the front speaker is a handy ignition switched cable that is meant for air con installations. Since I have no intention of fitting one, it seemed sensible to make use of it

One soldered bullet connection later and the feed to the relay is complete

The relay in position and the existing cable in the car now connected to the other side of the relay contacts.

Job done!!!

A quick test, after re-connecting the battery, showed that the headlights are now switched off when I turn the ignition off Result!!!

I may at some point re-site the relay and fuse for easier access should the fuse blow for any reason, but apart from that I am happy with the results

 

[Tom W]

That looks very neat. Nice to keep the proper colours so it all makes sense behind there.

My modern car has headlights that come on and go off with the ignition, but the function can also be overridden if the headlight switch is operated when the ignition's off. I don't know if this is a legal requirement but I guess you could achieve this fairly easily by having the headlight feed also switched by a 2nd relay in parallel with the 1st. This can be fed by a permanent live (piggybacked off the cigarette lighter?) through a discreet switch that could be easily hidden.

Tom

 

[codekiddie]

That looks very neat. Nice to keep the proper colours so it all makes sense behind there.

My modern car has headlights that come on and go off with the ignition, but the function can also be overridden if the headlight switch is operated when the ignition's off. I don't know if this is a legal requirement but I guess you could achieve this fairly easily by having the headlight feed also switched by a 2nd relay in parallel with the 1st. This can be fed by a permanent live (piggybacked off the cigarette lighter?) through a discreet switch that could be easily hidden.

Tom

You got me thinking there, so I just tried operating the headlights on our Ford Focus, and the only way they come on is if the ignition is on, so I guess not a legal requirement to be able to bypass it

 

[SydneyRoverP6B]

Very neat indeed Phil!

Ron.

 

[unstable load]

Before you install that, consider that the lights draw a significant amount of juice, so if your
battery is marginal then you may struggle to start in winter. My motorcycle has this feature
with permanently on lights and it sometimes catches me out. I am going to mod it to only
come on when it senses the alternator charging rather than with key ON.

 

[codekiddie]

Before you install that, consider that the lights draw a significant amount of juice, so if your
battery is marginal then you may struggle to start in winter. My motorcycle has this feature
with permanently on lights and it sometimes catches me out. I am going to mod it to only
come on when it senses the alternator charging rather than with key ON.

The point of the mod is not to allow me to leave the lights on permanently, but rather have them switch off automatically when I switch off the ignition. The side lights will still be on, but the current drain would be far reduced. If later I turn on the ignition and the lights come on, then I can switch them off in the normal manner before I crank the engine.

I quite like the idea of modifying it so that they will remain off until the alternator starts charging You could use the switched side of the ignition warning lamp to detect this, as it is connected to ground, (which turns the ignition light on), until sufficient charging is available. The only downside could be when driving at night and an alternator fault occurs, leading to no more charging of the system, and all the light go out even though the battery could quite adequately light them at that point, so the idea might need a little more fine tuning :?

 

[ghce]

One system I and another company toyed with a few years ago was an automatic battery lead disable. Admittedly the reasoning for the device was not as a headlight interlock but a way to stop all battery drain after the ignition was turned off allowing for long lay ups.
I can't see why this system would not work in the same way, the only proviso that has always needed inclusion is a specific bypass for the battery line to the radio permanent +12v input to stop the loss of preset radio channels every time the battery disconnects (only micro amp current draw) if you so wished you could also keep the clock enlivened however I would not as this is a significant current draw and self defeating to my original intent.

The device was inserted at the battery post and dependant on which design was used had only 1 other wire connected. All a bit in the dim past of about 15 years ago but maybe relevant to many classics.

Graeme