Head Lights with No Head Light Switch Using Ignition Switch

[david58]

I want to do away with the headlight switch completely. So any time the key is on I have head lights and running lights. Or better yet when the engine is running the lights are always on. I am thinking 4 relays 2 for low beam 2 for high beam, or would 2 relays do the job? What would be the best trigger to use so they are on when the engine is running and off till it starts?

Edited title of thread.

[Ol'fogasaurus]

I think it depends on what lights you are running. If you are running stock headlights and tail lights or even LED taillights then a dimmer switch should be good enough for the headlights and a relay maybe for the tail lights. The bigger the draw of the lights then you have to adapt to the draw protection remembering that there are other electrical draws, the size of the wiring any one draw is using and the length of the run http://www.nooutage.com/vdrop.htm. Also remember that the ground should be of the same gauge of wiring as the positive source wire.

I try to limit my draw to something less than what my charging system will put out (my preference). Also, add some kind of master fuse or circuit breaker to protect your electronics and especially to your ignition/switching source. My circuit breakers is just less than the 55 amp load that my alt puts out. I think there are at least 75 amp alts out there and maybe higher output ones than that. If you are going to draw more than that, use a second battery and appropriate wiring to charge both.

The bad thing about running everything off the switching source is that when starting the engine there is a big draw through the switch, maybe enough to stop starting and the potential of burning something out is there (a short?). The ignition switch will often have an accessory side and that I think protects the ignition but if everything is wired from it, it is still a lot of potential draw through that part of the ignition switch.

Some thoughts.

Lee

[Piledriver]

The later VWs use what is referred to as the "X" load reduction relay in the schematics.
This kicks off the lights etc while cranking.

Simply running the lights off the fuse box input wire>relay makes a huge difference in brightness, the headlight switch on my Pile only controls the relays. (the early 914s had issues with burning out the now unobtanium light switches, this is the cure)
If you are simply "eating" light switches, the relays themselves are the cure, as long as the light switch only controls the relays.

If you still have an "X" relay, use it as the source.
If not, it would easily be added.

Even on modern cars where the headlight stay on all the time, they are still interlocked to the parking brake or something so there IS a way to turn them off. Can come in handy in some situations.

[Ol'fogasaurus]

I have been seriously thinking about switching relays off and on with the ground in my next project.

I agree with using the relays when necessary but it is the “switching” that I was referring to along with the KISS theory. Too many un-needed relays are also not simple.

If this is dual purpose, street and off-road, then you have some things to deal with. Proper headlight rules; e.g., DOT, state, county, city, development, block, street, household, marriage, etc., add to that the laws on min and max height, number facing forward that can be run on the street at any one time plus how they are hooked up, number facing to the rear and when and “when’t” they can be on that you also have to deal with. The other is aux head lights, for an example, which are also predicated on the above rules.

This is over kill in some states, not enough in others.

I thought this build was to be a quick on and off the pan build, but then the competition with doc raised its pointy little head so this as an attempt to: Simplify, simplify (Henry David Thoreau).

Lee

[david58]

If you still have an "X" relay, use it as the source.

Do you have a part # ?

[Piledriver]

If you still have an "X" relay, use it as the source.

Do you have a part # ?

No, it's a std 4 prong NC relay.

The std ignition switch has a circuit that keeps it "on" in run, but it turns off in "start".
I'm reasonably sure the T1 std ignition switches have that as well.

If you aren't using a std ignition switch, the easiest way to duplicate the function would be to find a 12V SPDT relay, with NO and NC contacts, and set it up as described, using the NC contacts and a starter input.

[Dale M.]

Simply put a relay in place is light switch and "activate" relay (through winding) with power from ignition circuit (any circuit that turns on with key)..... You can use standard dimmer relay to switch between high and low beams....



Just put relay in place of DPST switch in graphic.... You can actually not use fuses in graphic and run relay(s) outputs standard fuses already in VW standard fuse block....

And use relay like one shown in bottom right with two terminal 87 (one to head lights one to tail lights).... For a fee ( big one) I can draw custom graphic with colored wires and all....



When you think about it basically light switch really only turns on off lights through duplicate sets of contacts that are all slaved together ...

The only gotcha is in most cases main hot wire goes to light switch then to ignition switch so you have to maintain that continuity path ....

Also you may want to add a NC closed relay that actually opens "control" to "light" relay during starter cranking....

Activation of relay by switching 12 volts (positive(+)) or ground (negative (-)) control is just a wiring scheme to really only pleases the guy doing wiring (or some computer logic) ..... Relay operation is the same....

Dale

[david58]

I had put this on the back burner so I could get the wiring harness in the car and get everything hooked up except the ignition switch and the turn signal switch. Well I am to the point now that I need to get the lights working. I have bench tested the lighting and everything lights up.
I am using a 1972 912 steering column. I have searched high and low for the wiring for those 2 switches.
Here is what I have. It is a 7 wire Ignition Switch.

Here are the Wire colors it has. And testing it with an OHM meter this is what I came up with.


Large Red wire = Power into switch
Large Yellow wire = Starter Input
Medium Red wire = Power Key On Only (Use this to turn on lighting)
Large Black wire = Power Key On and Start
Small Gray wire = Power key Off Only (most likely for dome light)
Small Gray wire with Red Stripe No Continuity to power (most likely for key buzzer)
Small Black wire = Power Key On and Start

Any input here will be greatly appreciated. And thanks to everyone for the advise.