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backwards wiring from factory?

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My harness has never been cut into, but My headlight wires are not correct.


My car has 4 lights in the front, 2 low/ultra low beams on the outside and two high beams on the inside.


According to the service manual, there are two fuses, one fuse for High/low beams onthe right side, the other for the lights on the right side.


driver positive is supposed to be R/Y for both


passenger positive is R/W for both




My driver high beam is R/W, low beam R/Y


Passernger High beam is R/Y, low beam R/W




WTF? The wiring diagram in the book says R/Y should only be on one side and R/W should only be on one side........

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The headlight plugs can be pushed out and moved. Do you have the stock square headlights from Nissan or are they after market? perhaps with metal back side reflectors? Those tend to have the housing grounded and when plugged in will blow the fuse. A PO may have swapped the wiring around to fix this.

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I do not know how it is should be.  This is what I have found on my 521 trucks.

There is one headlight fuse.

Red is power to the headlight switch.

Red with a Yellow stripe is power after the switch, before the headlight relay.

Red with Black is low beam power between the relay, and the lamps

Red with White is high beam power between the relay and the lamps.

Black is headlight ground, and has a wire back to one of the bolts that attach the voltage regulator to the inner fender.


This is what I believe to be true on some early 510 cars.

There are two fuses. 

Red goes to one side of the car, Red with a Blue stripe goes to the other side of the car.

The headlights have switched grounds, that is they are always "'hot".

The Red, or Red with Blue goes to the common terminal on the headlights.

Red with Black goes from the low beam headlight, to the headlight relay, two separate Red with Black wires, one for each side.

There is a "Y" near the headlights joining the two high beam lamps together

Red with White goes from the high beam headlights, to the headlight relay, two separate Red with White wires one for each side. 

Remember these are still hot wires.  The relay switched between the red with black, and red with white wires. 

After the relay, the wires are Red with Yellow, going to the light switch. 

The light switch, when turned on, connects ground to the red with Yellow wires.

I do not know exactly where the light switch ground is.

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power comes in on the R/Y (R/W for passenger side) directly from the column switch, after the fuses, according to the manual. Then switching the high beams switches the relay, which switches which lights receive ground (on R/G for the high beam circut, and on R for the low beam circut)

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The issue I am having is that the low beam on the driver side is dim, might just be the ultra low beam lighting up actually, I have to recheck with the test light.


Then when you go to the high beams the driver side works totally normal, and the passenger side just keeps the low beam illuminated. (possibly the ultra low too, I have to check this also)




Perhaps what I should be asking right now is "does the backwards wiring matter and does it contribute or have no effect on the issue"



Does it really matter which headlights get their power from where?, No.


Could this be causing both issues I am having, if getting no power on R/Y? Yes.




Anyones thoughts are greatly appreciated.

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"Blk wire by the volt reg? EZ to ck I guess just unscew that wire and see if lights woirk.
I think there is a ground wire by the hood release also. 510s"


Easy to check if you have  a 510, I do not.  somebody want to give me one?


On my 521 trucks, if I remember correctly, there is one lug, that has two wires, and possibly another single lug, at the voltage regulator.

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what is ultra low beam????????

on the standard USA spec lamps(outers) there is 2 elements in there . In 510s there is 2 35 watts elements.I assume the lamps are the same 3 prong set up. when you go to high beam the outer lamp will use the other element when the ground is switched in the 3 prong plug.

High beam will have 12volts on both sides then one goes to ground and the lamp comes on.


have you tried swapping the lamps to see if the proplem moves. could be a connecter loose or corrosison issue.



The wiring is not the same as a 510 or a 521.

510 and 521 work different.

But most Nissan cars/Toyota trucks are the same its a swichable ground so it is the same.



I have a H4 haness in my 521 but my outer lamp is dim also. but notice my connector pin is burnt black(arched) so if I move it around the lamp gets brighter

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Yeah I was thinking that too. Could be for an 810/910 instead of a maxima/910, they do have some slight differences.


However that still doesnt explain what in the hell is going on. I am going to start backprobing wires by cutting open areas of the harness. If I am not getting power through R/Y, that only explains some of the problem.


I know one thing for sure, this fu*#^ng sucks.


But I did buy the car like this....

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The issue I am having is that the low beam on the driver side is dim


Then when you go to the high beams the driver side works totally normal, and the passenger side just keeps the low beam illuminated.


Could be as simple as an old bulb. Have you tried swapping the two low beams?
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If I am not getting power through R/Y, that only explains some of the problem.


ck by the light highbeam relay first.the connection there and wiggle the relay if you have one.



key is was this all working before correctly?

If YES then its a corrossion issue or soemthing loose or lamp.

Or was bad when you got car then could be hacked wiring(then open up the tape but not before)

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no, when I got the car the lights did this same thing. I am fairly certain there is a fault somewhere I am going to have to repair. The wiring has guaranteed to have never been taken apart before.


I can not light a test light at the terminals, its definitely in the wiring, not the bulbs, not the terminals, not something loose.


Power comes directly from the column switch and does not go through a relay. And I have power at the column going into the harness.


It also shows power on my multimeter, if I ws going off the multimeter alone, The system would show all good, but when I use the test light, a different story....

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I can not light a test light at the terminals



It also shows power on my multimeter, if I ws going off the multimeter alone, The system would show all good, but when I use the test light, a different story....

So you have power at the bulb socket, but test lamp fails to light. These symptoms are a classic sign of a loose or dirty connection: power that disappears under load. This calls for a voltage drop measurement. Give close scrutiny to the ground wire in the socket too.
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Something that is likely going to screw you up is that test light/volt meter, you see every time you test for power on a wire, the other volt meter wire is likely going to a ground for the test, well you just added a ground that is not supposed to be there, and that really screws these 80s harnesses up.

Make sure all you headlights are glass, no aftermarket ones with metal backs.

Make sure you have not added something like a aftermarket gauge or a radio with a light in it that you tied into the lighting system because you wanted the light to come on with the headlights.

Also adding foglights to the headlight system is bad, you cannot grab power from the headlight system because to make whatever you added to that system work, you have to introduce a ground that is not supposed to be there.

When you add a ground, it screws everything up, as an example I put a 720 harness into my 521, once I had everything wired for round headlights and it worked, I also wanted the brights light in the dash to work, in the 521 cluster the brights light is a ground, that tiny little light screwed the whole thing up.

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The grounds are good all the way to the relay and past. I tested the ground circut on high and low beams on all the light sockets and it is great, but dim test light every time on the Red/Yellow wire.


There are only two places R/Y goes, it comes out of the column switch (good power there) and a lead goes to the high beam indicator along the way to the headlights, which recieves ground when the high beams do.



Not sure on the glass housing, I think they are, I will check. The problem presents itself when there are no headlights hooked up at all though, so I dont think it has anything to do with the lights themselves.

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Captain, when you say "power" what do you mean? Voltage is present? Or that the test lamp lights up?


The problem with a test lamp is it won't tell you how much voltage is there. A 1v drop will still light the lamp. A voltage drop test is the real test: with the lamp in place and ON, measure the voltage between

* Battery NEG terminal and lamp ground

* Battery POS terminal and lamp +

If the voltage is more than 0.1 v, that's the problem. There is always going to be some drop cause wires have resistance.

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by "power" I mean battery 12v+.


I am saying that at the R/Y, it is barely even lighting up the small test light. But I am showing 12v, I will do a drop test when I go back out to work on it.


I was mistaken earlier in saying that is has "ultra low" beams or "day lights", It just has dual beams, they stay at the same illumination when you activate the center beams. I was mistaking that the outer beams were supposed to dim when the high beams were lit. Mine are doing this as an effect of the absence of enough power, resulting in extremely dim low beam and no high beam on the same circuit.

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