Headlights on with ignition

[evan9eleven]

So I tried to search, and found lots of info and diagrams/pics of the headlight switch. I also have the Bentley manual, but I've not found a post by anyone who has wired a US-spec car for headlights/taillights that come on with the key. I believe cars in Canada all do this, and here in Scandinavia it is the norm, so it would be nice to make the change so I can stop forgetting to turn the lights on now and then.

My car is an '81 SC.

Thanks in advance for any suggestions!

[T77911S]

there is a mod that is quite good, i have done it myself, where the normal current path for the headlights is used to activate 2 relays for the headlights. this diverts all the headlight current from going thru switches to going thru relays. if you did this, it would be easy to also re-wire for ignition operated headlights.
you could also just add a 3rd relay that is activated by the ignition switch that passes the headlight control signal thru it. all this could easily done so as not to butcher the original wiring.

[evan9eleven]

Originally Posted by T77911S

there is a mod that is quite good, i have done it myself, where the normal current path for the headlights is used to activate 2 relays for the headlights. this diverts all the headlight current from going thru switches to going thru relays. if you did this, it would be easy to also re-wire for ignition operated headlights.
you could also just add a 3rd relay that is activated by the ignition switch that passes the headlight control signal thru it. all this could easily done so as not to butcher the original wiring.

Thanks! I was planning on doing the headlight relay kit anyway, but I hadn't considered a third relay to neatly control the "always on" setup. Great suggestion!

[arrivederci]

I'm no electrician but I did install one of the relay kits in my '72 this weekend. It really only interrupts the signal from the headlight switch - one relay for low beam, a second for high beam. The relays do nothing unless the headlights are first turned on from the switch. My guess is you would need to wire something further upstream from the relays/fuse panel to switch the headlights on with the ignition.

You are basically going to connect an ignition switched power source to the power line coming out of the headlight switch.

[theiceman]

i wouldnt do this ....

but just to clarify .. you are talking about DRLs ,, daytime running lights.. they are on all new cars in Canada for about the last 25 years or so . This was not mandated in the days of the SC thats for sure and my SC doesnt have it .

The reason you want to be very carefull is that you want the lights on AFTER the car is started. the last thing you need on a cold morning is to have that last bit of juice that may have started your car to get sucked up by your lights when you try and start it . i am not sure the SC has the inteligence to just start the lights after the car is running , unless you build it in.

[evan9eleven]

Actually, I am not talking about dedicated DRLs. Here in Norway on most cars of a certain age, when you start the car all the exterior and dash lights come on including low beams, same as turning them on manually. You have a good point, its not ideal if the starter is sharing battery cranking current with all the lights. A good design will be important here...

[arrivederci]

Originally Posted by theiceman

i wouldnt do this ....

but just to clarify .. you are talking about DRLs ,, daytime running lights.. they are on all new cars in Canada for about the last 25 years or so . This was not mandated in the days of the SC thats for sure and my SC doesnt have it .

The reason you want to be very carefull is that you want the lights on AFTER the car is started. the last thing you need on a cold morning is to have that last bit of juice that may have started your car to get sucked up by your lights when you try and start it . i am not sure the SC has the inteligence to just start the lights after the car is running , unless you build it in.

Actually, many things on the car are not hot when the starter is cranking. Not sure how it is done, but I found out first hand when looking for a hot-while-cranking source when wiring a 3.6L harness into my car. For instance, the cig lighter is hot with the ignition on, but shuts off while cranking. So it can be done, just test carefully.

Even though you don't want DRLs, do a search on them. I bet there are clear instructions on how to do it that could get you started in the right direction. I remember hearing about a generic add-on module that handles all the complexity for you.

[T77911S]

Originally Posted by evan9eleven

Thanks! I was planning on doing the headlight relay kit anyway, but I hadn't considered a third relay to neatly control the "always on" setup. Great suggestion!

i left the power source up to you.
no, its not a good idea with these cars for the lights to be on when cranking, they have a hard enough time as it is.


unless you put in 4 relays you would only be able to put it on the low beam side, or get a double throw relay that will open both hi and low beam signals to the headlight relays. personally i would just put one rly on the low beams. i rarely use my hi;s and i certanly would not leave them on.

[bourgeois911]

How about a time delay relay? Seems like an assortment of these sorts of things out there.