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Headlight crossover.

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Question for our ratsun virtuosos.  How much cross over is there in the headlight systems of older Datsun wiring for models that had 5.75in sealed beams?


Obviously there is differences between single and double headlights.  For the purposes of this question lets assume Pre '75 dual headlight models like 410/411, 510, 521 etc.


I expect some differences of course but wondering if they are major or minor.


**EDIT**  - I should add I am referring to the electrical system aspect of these cars too.

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Crossover? do you mean similarities???


The 620 had one side of the bulbs grounded and the power was supplied by a relay that chose hi or low by a dimmer switch in the turn signal arm. In '78 this changed and the relay was removed and the hi or low was selected directly from the dimmer switch on the turn signal arm.


The '74 610 and 710 had power supplied to all bulbs and the relay chose hi or low by selecting the proper ground. Almost exactly opposite to the early 620.


The '78 810 is the same as the 610 and 710 above.



I don't have every FSM other years of 610/710 may be different?


If the 620 changed to ground switching in '78 maybe others like the HL510 and the S10 (200s) did the same.


From '80 on the headlamps were rectangular and wired differently.

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Datsun Mike should respond to this.  Some models applied +12 to both filaments and switched ground connects to select the proper high or low beam.  Others applied fixed ground and switched +12 volts to select the proper filament. Big difference in wiring harness!

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Thanks.  Yeah similarities.  I am working with a company to develop a headlight kit to modernize the 510 headlights and was curious as to what other vehicles it could be adapted for since a lot of them use the 5.75" (6") sealed beams that will be replaced.

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All 5.75 headlamps are the same. Either they are all powered up and the ground is selected for turning them on or all are grounded and power is sent to turn them on.


The biggest improvement to the lighting is heavier gauge wiring with relays and fuses, to shorten the distance between the battery and the lamps. This lowers any voltage drop and allows heavier draw halogen bulbs (or other) to be used.

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That is true.  The goal here to eliminate the sealed beams for true bi-xenon HID's with true HID projectors and not halogen ones (I researched what are the common retrofits for the 510's so I have that part covered.) and to provide a wiring/relay setup that involves minimal effort.  I got started on this mainly cause my cars lights are horrid and the factory wiring leaves a ton to be desired so I figured a whole harness replacement with something that uses modern shielding, connectors etc and is all and all aesthetically beautiful or well as beautiful as a wiring harness can be.  Working on Porsches kinda made me OCD on wiring.  The wiring on the air cooled cars was terrible too and I ended up spending so much time rewiring cars that whenever I see a mess I can't help myself lol.   It may turn out to be a one off harness but I like to share and if I can spread it across other models then all the better.  I was hoping that the the only major difference is the length of wiring which means if it does become a product the price can be reduced as it covers more models.  Anyway that said with my first child days a way it may be a few weeks :P

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Why not just develop a complete wiring kit that takes the headlight power and high beam power and is all new from there - under the dash.  Build your own sub-harness with relays and the like so you just have 2 power wires and a ground to hook up.  No sense installing all the greatest new technology and then rely on an old wire harness.  This allows you to set it up however you want.  

Don't reverse engineer the old crap.  Just engineer.   :thumbup:

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Not under the dash, the new wiring length would be the problem. Run heavy gauge wire through fuse to the headlamps direct from battery and use the existing wiring to run the relays that ground to turn them on. All heavy gauge wire including the ground. All short runs to limit voltage drop to minimum.   

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Here's an example for a 510 headlamp set up. All that you see is mounted on the rad support with The power going to each lamp through the shortest distance possible to reduce voltage drops. The thicker the wire the better. As the current flow is the same in any part of a circuit the ground wire must also be heavy gauge to match.


This uses the very poor stock wiring to switch the newer relays. Saves a lot of wiring. For relays the '80 and on 720, S110, S12, Hardbody and Pathfinder has oodles of relays. The blue ones look like the right ones. (there are black and brown so get the right ones) And get the plug in the back and trim the wires long.



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I made a new headlight harness for my 510. The power wire coming off the pull switch is the relay signal. The low beam relay is grounded always, and the high beam relay is grounded by the high beam ground wire from the stalk. The lights are bright but I am still running sealed beams, so I take it for what it is. Still an improvement over stock. I also eliminated the low beams dimming when the high beams are switched on, so I have full output. Between the new low gauge wire, relays, and a good alternator, amp draw isn't an issue.

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The lenses of low/high beam bulbs and high beam bulbs are cut differently. Low/high bulbs spread out more light, where as high beam bulbs focus the light more on one spot. Is that really necessary? Depends I guess. I have had thoughts of swapping low beam bulbs in for high beam bulbs, so I still technically have high beams, but with more spread out light. But I think that is only an "option" because of my wiring method above.

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So the kit I think means no more to having to bash the crap out of the side wall to fit the E30 housing in place of the sealed low beam.  This is because the HID projectors don't stick out as far from the e30 housings.  Or well least in my test fit I didn't have to but we will see when I actually bolt everything down.  The kit also comes with a Morimoto harness that has two relays one for each HID light.  The high beam solenoid can be wired into your highbeam wire to trigger the shutter if you want bi-xenons.   The kit is avail at www.squaredmotorwerks.com for 375.00 It comes with the light adaptors, ballasts, projector housings, bulb kit, and the harness. It comes in two shipments as the Morimoto stuff is dropped shipped.  You can also order just the adaptors separately if you already have the lights that is.  I don't work for them or anything I just offered to be the guinea pig for doing it on something other than an E30 BMW. 


I have a video coming soon with a walk through of how to put together the kit and once I finish rewiring my car I will do a video on the install.   My car wasn't as well sorted as it looked in the ebay add.  It looks like a 5 year old wired it prior to my buying it so I am having to gut the cars wiring completely.  So stay tuned for some vid/pics of the final install.



****EDIT  I should add that this kit uses REAL hid prjectors and cutoffs and doesn't blind oncoming traffic from the glare caused by running HID bulbs behind a halogen projector or worse no projector.  So you can actually see where you are going and don't have to worry about being involved in a head on collision because you blinded oncoming traffic.

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