Create daytime running lights w/relays?...

I have an '82 Datsun 280zx non-turbo GL.  I want the headlights (preferably high beams) to come on (preferably at about 50% power) whenever the car is on as daytime running lights.

I bought a module that was supposed to accomplish this, but found it wouldn't work with my car.  A tech at the company that made the module told me it won't work with my car because the same two wires leading from my headlight switch are always hot whether the switch is in the high- or low-beam position.  He said the beam is switched by a relay under the hood.  I sent the module back.

I'm thinking I can make this work with simple relays (I know I may not be able to control the brightness of the beams, but I can live with that).  I have a complete set of tools, a factory service manual and just enough knowledge of electricity to ruin my car.  I have a basic understanding of relays.

Can anyone give me some advice on this?  I'd really appreciate any help.

cant really help you out with the relay question, but it is nice to see another Datsun fan here...I have a 79 ZX, a 71 240 and a 77 280...

good luck...

well, for a bare bones simple set-up....

87 - 12v fused

85 - ground

86 - switched 12v from ignition

30 - out to hi-beam wire

87a - not used

add a heavy duty resistor to the 30pin output for lower voltage.

Thanks for the advice! But I think it may not be that easy for my car. Please read on:

I think that there will be a problem. I was told that a relay under the hood switches between high and low beams by switching the grounds from the headlamps.

You see, on my car, the same two wires (each of my headlights is on a separate fuse) are hot (approx. 12v) whether the switch is in the high or low beam position. (I know I will need to relays to keep the headlamp circuits separate.) Switching from high to low or low to high causes the under-hood relay to switch which beam is grounded.

So, if I wired as you suggested--tapping the 30 of each relay into the wire that is hot, I think it would cause the low beams to light. That is presuming the under-hood relay normally has the low beam grounded.

That might actually be better. Hi beams can be annoying, and I don't know if I really want them to light. I think a lot of the daytime running light modules sold light the high beams so that the life of the low beams is not shortened by continuous use.

But isn't there another problem? If I hook it up your way, what happens when I turn the headlamps on at night by their normal switch? Won't they be getting power from 2 sources--the normal source AND the 30's on the relays? I don't know enough about electricity to know if this is a problem, but I presume it is.

If it is a problem, will I need diodes and/or other relays to somehow shut off the relays I'm already installing whenever I turn the headlamps on? (If so, I may be in luck as whenever you switch the headlamps on, a third wire goes hot. I think it was for the optional driving/fog lamps. I guess I could use it to trip the relays that would shut off the initial relays.)

I know this is confusing, but your suggestion is really helping me to think this through. Some more input from you, and I think I can do it!

Lee, yes having two + feeding the headlight circuit would be bad, you would more then likely blow a fuse every time you turned on your headlight switch. I would add two relays. one to shut off the initial relay as soon as then in 12 volts to your parking light wire so that there is no chance of there being to 12 volt feeds at anytime to the headlight wires. I would also install a relay to allow you to idle the car with the DRLs off. I would use the parking brake to be your off switch so that you could set your parking brake and your DRLs you shut off.
Here is what I would do.

RELAY 1
85-ground
86-connect to the wire that powers your brake warning lamp.
87a-12 volt fused
30-to pin 87a on relay 2
87-not used

RELAY 2
85-ground
86-parking lamp wire +
87a-in from pin 30 on relay 1
30-out to pin 87 on relay 3
87-not used

RELAY 3
85-ground
86-12 volts with key in run
87-in from pin 30 on relay 2
30-headlight wire

If you want to use you high beams we could rework the relays so that they supply ground to the wires coming out of the factory beam selector relay. Let me know if this works for your or if you realy want the high beams on, but I think the way it will work this the setup I wrote out is that the beam selector switch will control even the DRLs.

Keep me posted

Ken

I just reread the post I just summited and notice a few typos, sorry I am dead tired but wanted this to be here for you first thing this morning.

Ken

i stand corrected, brain fart on my part. my bad...but gotcha thinking, so it atleast did that :)

Ken has the way to go, after thinking about it yesterday at work, i was like DOH! how stupid of me.... and basically came up with what Ken has. Just that relay 1 i used the ground of the parking brake, same difference...lol

Thanks so much or the responses.  While I was figuring this out, someone from a Z board I had posted to contacted me and told me he sells a European replacement for my 7" headlamps.  It uses an H4 bulb and also has a spot for a BA9 bulb that can be as much as 20w.

So I've ordered two of those.  This method seems superior to me because not only will it involve easier wiring that does not interrupt the existing headlamp circuit, it will also not use the life of those beams.  I could get a ticket for a burned-out headlamp (which is a moving violation in CA now), but since DRL's are not required on my car it would be no problem if they burned out.

I definitely will incorporate the parking brake suggestion.  I really like that idea.

Will I need any diodes or relays with internal diodes for this setup?  I really still don't quite understand when and why either of these is used.

Thanks so much for the help.

Oh yeah, why would it blow a fuse every time I turned on my headlights if I two +'s feeding it?

i dont know what people are trying to say but there is so much easier ways if its ground that simple just as pos whould be as well . you have to test simple at the bulb in the two positions if there is two wire that what most likely is happening is the pos and neg is switched between the two wires ex
:   lets say the red is pos and the green is neg  for low beams so the opposite whould be  the red being neg and the green being pos from high beams .

do this test the wires at , atleast one of the bulbs and let me know you dont need two relays and if you do whatever but email me personally and tell me your findings. i sware most people answer and dont remember that not only relays isolate wires diodes do as well and and i also guess some dont know how relays really work so you want this prob solved cheep and affective email me with all info i asked and i will be glad to assist.