Ultimate Headlight upgrade: DOT Legal LED Headlamps!

[Ben's Z]

To be honest I worked for Truck-Lite and sold these headlamps about 2 years ago. Never once did these lamps not just plug in in place of a 6014 or 6024 headlamp and work just fine. I may have misspoke. I believe he said that when I pulled the headlight switch the female spade in the other terminal went to about -11 volts.

You have still not answered my question as to why on this car these LED headlamps do not simply plug n play, but on any other car, truck, jeep Mack truck at Waste Management and Allied Waste, they plugged in and just worked. Something is different about these datsuns.

I have studied the wiring diagrams from many of the FSMs, especially after others pointed out to me that the 70 & 71 240Zs have their headlight circuits wired differently than other S30s. I have converted both of my cars to relays for headlight controls. I do know what I'm talking about, and yes, I am an electrical engineer.

I'll step you through the circuit, using a positive to negative convention.

1. 12VDC+ comes into the combo switch on the right using a White/Red wire.

2. When the headlight switch is in position 2, it completes the contact and goes out the Red wire. (See the first attachment.)

[ATTACH=CONFIG]45745[/ATTACH]

3. The red wire goes into the fusebox and goes through two fuses. The fuse for the right headlight has a Red wire. The fuse for the left headlight has a Red/Yellow wire. (See the second attachment.)

[ATTACH=CONFIG]45746[/ATTACH]

4. The Red and Red/Yellow wires travel to their respective headlights and land on the common pin for the headlights. Two wires come out of each headlight. One wire is Red/Black. The other wire is Red/White. The two Red/Black wires join as do the two Red/White wires. (See the third attachment.) The wires then go back to the combo switch on the turn stalk.

[ATTACH=CONFIG]45747[/ATTACH]

5. If the switch is in the low beam setting, the Red/Black wire will be connected to ground via the Black wire. If the switch is in the high beam setting, the Red/White wire will be connected to ground via the Black wire. (See the first attachment.)

At no time does the polarity change. The path to ground changes.

Since the D in LED stands for diode, yes, polarity is important. Did the headlights come with instructions? Look for any guidance on wiring. My guess is that the common pin is supposed to be grounded, as I said before.

If you still don't believe me, take the voltage readings at the headlights again. However, take out BOTH headlights. With the switch in low beams, you will find that you have 12VDC (probably less) between two of the three pins. When you change it to high beams, the pin that was positive before will still be positive. The negative will go to the third pin.

[Arne]

Something is different about these datsuns.

Yes, they are different. They used switched ground as noted above, not switched power. For normal filament type lights, it doesn't matter. But diodes (the D in LED) are by nature current-direction sensitive. To use those lights you'll need to reverse the switching polarity using relays.

[SteveJ]

To be honest I worked for Truck-Lite and sold these headlamps about 2 years ago. Never once did these lamps not just plug in in place of a 6014 or 6024 headlamp and work just fine. I may have misspoke. I believe he said that when I pulled the headlight switch the female spade in the other terminal went to about -11 volts.

You have still not answered my question as to why on this car these LED headlamps do not simply plug n play' date=' but on any other car, truck, jeep Mack truck at Waste Management and Allied Waste, they plugged in and just worked. Something is different about these datsuns.[/quote']

To be honest, I did answer your question, as did Arne. I said

Switching polarity? Nope. They don't. The stock wiring on the 280Z has the 12VDC going to both headlights. The return wires go to the high/low beam switch. That switch selects the path to ground. Look at the circuit that Daniel Stern uses to demonstrate the value of relays. Note that the ground is common and you have two 12VDC sources coming in.

If your LED headlights require a common ground, you could put in relays that utilize a common ground. If you don't understand what I'm saying, let me know, and I'll draw up the circuit for you.

Arne said

Yes, they are different. They used switched ground as noted above, not switched power. For normal filament type lights, it doesn't matter. But diodes (the D in LED) are by nature current-direction sensitive. To use those lights you'll need to reverse the switching polarity using relays.

If you look at the link I posted, you will see the circuit has 2 (two) 12 VDC+ wires and a common ground.

If you look at the wiring diagram for your car (or the images I posted), you will see 1 (one) 12VDC+ wire and two wires that could go to ground. You select your path to ground with the high/low beam switch.

I understand perfectly well what is going on. I offered to draw up the relay circuit for you. I can't help it that you don't understand.

Just buy the relay kit in the Black Dragon catalog. If you figure out how to wire it in, it will fix your problem. There is a way to fix your problem without installing relays, but it involves re-wiring your switch. I wouldn't recommend going down that path.

[Ben's Z]

Sorry guys my electrical skills and knowledge are limited to rewiring boat trailers etc.! I understad it now. Is the black dragon kit hard to install?

[SteveJ]

If your electrical skills are lacking, it could be a challenge. You could also contact Dave, aka Zs-ondabrain. He has designed a plug & play for the 240Z. I think he has also made a few for 280Zs. Given the choice between the two, I'd pay extra for Dave's if I were you. You will receive better instructions and support.

[Ben's Z]

Yeah black dragon's website for looking up parts is complete garbage. Someone should tell them it is 2011. Does his kit look ok in the car? Is it completely noticeable? Anything particularly unsightly?

If your electrical skills are lacking, it could be a challenge. You could also contact Dave, aka Zs-ondabrain. He has designed a plug & play for the 240Z. I think he has also made a few for 280Zs. Given the choice between the two, I'd pay extra for Dave's if I were you. You will receive better instructions and support.

[SteveJ]

Yeah black dragon's website for looking up parts is complete garbage. Someone should tell them it is 2011. Does his kit look ok in the car? Is it completely noticeable? Anything particularly unsightly?

Ben, you're trying to install led headlights in a 33 year old car. Don't you think that draws some notice? I don't have pictures of Dave's relay design installed, but I do know that a lot of people are happy to have them.

[Arne]

Dave's kit is made for 240Zs with square plugs. In a 240Z it is total plug-n-play, extremely well made, and not obtrusive-looking at all. (And I'm a bit fussy about that kind of thing.)

For a 280Z, you'll need to contact him to get him to make one that lacks the round connectors that the 280Z uses. Still a great option, just a touch more work on your end.

That would still be way better than the Black Dragon kit, as people who have tried that in the past have said you'll need to cut and splice the new relay harness, as it is really a generic part that doesn't truly fit our Zs all that well.

[Ben's Z]

Arne,

I found BD's kit last night and it said no splicing all plug n play, not true eh? Thanks for the heads up, I almost ordered it.

Dave's kit is made for 240Zs with square plugs. In a 240Z it is total plug-n-play, extremely well made, and not obtrusive-looking at all. (And I'm a bit fussy about that kind of thing.)

For a 280Z, you'll need to contact him to get him to make one that lacks the round connectors that the 280Z uses. Still a great option, just a touch more work on your end.

That would still be way better than the Black Dragon kit, as people who have tried that in the past have said you'll need to cut and splice the new relay harness, as it is really a generic part that doesn't truly fit our Zs all that well.

[SteveJ]

The BD kit does have some glaring shortcomings since it is generic, and the relays are not standard relays. The there also aren't inline fuses, so those should be added. I bought the kit and proceded to replace most of it. The only good thing about it for you would be the fact that it has separate positives for high and low beam with the ground being common, so it would have worked in that respect for you LED headlights.