Headlight wiring question

Short answer no, long answer is yes if you carry a fire extinguisher.

Assuming you've got an American z31, are you going from sealed beams to H4 semi sealed and want to go with 100w's straight away, or are you going from 60/55w's to 100w's?

If you haven't already, go for the 60w H4's before you go out and buy a relay kit, or make your own relay harness up.

EDIT: In fact, run a relay kit BEFORE you put 100w bulbs in, it might improve your light output substantially. It did on my friend's R31 Pintara (I4 skyline) central spotlights.


The spotlight on the left of the above image is standard on early R31 skylines with the RB30E, but not on Pintaras with the CA20E. Friend stuck spotlights on his Pintara used a relay off the battery using the highbeams as a trigger, and his headlights were miles brighter than the stock ones on my R31 Skyline.

Definitely set up a good relay'ed system before trying to go higher wattage bulbs. I did a relay setup on my old daily driver ( mk2 jetta w/ 7" rounds) and the difference in light output was INCREDIBLE. It's on the list for stuff to do for the Z when I start working on it again.

right now i have sylvania ultra brights i got from kragen for 20 each but they have a defect that crack the light (why i am doing this now). I dont want to replace it with another light that will break 2 weeks after i put it in again.
Been looking at some cheapies off of ebay with the option of 55w 35 w and 100w.
Honestly i know nothing about wiring a relay into anything. Is there a relay harness for dummies book? haha

It's pretty easy when you break down how a relay works. It's just basically a switch that's turned on remotely.

I can draw you a Diagram if you wish. It's actually pretty simple to do. A little time consuming to do it right though.

A relay is a high-amperage switch that is activated by a low amperage switch.
the two circuits never touch each other, thus one just tells the other to turn on.


On a normal 4 or 5 prong automotive relay, you will have the following numbers:
85 coil wire
86 coil wire
30 hot wire
87a normally closed
87 normally open

Numbers 85 and 86 are the "coil" wires. If you wire one side to anything over 9 volts, and wire the remaining side to ground… the relay "clicks". It doesnt matter which one gets positive and which side gets negative. as long as there is one + and one -.

Number 30 is the CONSTANT HOT wire, and is always getting power. You run a wire of the appropriate gauge for the amperage draw (with the appropriate fuse in line) to the terminal, most often straight from the battery if it's a high power draw device like headlights.

Now you have 85, 86, and 30 wired up… so you have the 87 and 87a remaining.

87a is ONLY functional if your relay has 5 prongs. It is the normal resting place of the relay. That means anything that goes through terminal 30 will be present on terminal 87a. Regardless of whether or not any other wires are connected. You can think of 30 and 87a as being two wires joined by a paper clip. They're connected.

87 is normally open. No power runs to this wire. If you connect a power source to terminal 30, it will NOT be seen on 87.... so how do we direct power there?

A relay is a switch that activates a switch. So when you wire 85 & 86 to power and ground, it changes the direction of power going to terminal 30 from 87a to 87. Or if you have no 87a, it merely sends power from 30 to 87. It's as if you're removing the paper clip between 30 and 87a, and now connecting 30 and 87.

So in short, when you connect 85 and 86 to power and ground, you switch power going through terminal 30 over to terminal 87. If you have a terminal 87a, that will always get whatever terminal 30 is getting until you tell them to switch (by using 85 and 86). At that point, 87a turns off, and 87 turns on.




I'm only writing this because discovering the use of relays makes controlling electric flow and high powered wires in your car a lot safer. When you're in doubt on whether or not a relay is needed, just use a relay with a fuse on the wire going to terminal 30. You'll pat yourself on the back and you'll be happy to know there will be far less chances of something catching fire.

There are two ways of doing it, one way using 2 relays (one for highbeams, one for lowbeams) and another way using four relays (one for highbeam and lowbeam on each headlamp)

As for a plug and play kit… I'm looking for one.

Here's a diagram.

Alright thanks a lot seems easy enough. are 85 86 87 numbers you made up or are they a standard? Does it matter which side of the bulb is wired? or as long as they are on the + and - and not the ground they are ok?
i am guessing 20 amps is a safe amount to run through stock wiring with 30 amp relays?
This double relay setup is a bit safer right? id rather spend a few extra bucks on a relay and fuse than have no more car.

Wow, you're right, you really don't know much about relays, or electricity in general. No offence, it can be pretty confusing.
Okay, for ease of explanation, - wires pretty much bolt straight to the body. Chassis ground is negative.
If you're running relays, you're not running 20 amps through the stock wiring, that's the point of running a relay.
Two 100w bulbs at 12v will draw 16 2/3 amps, at 14.4V (engine running) its a 13.8A draw.

The double relay setup is necessary for highbeam/lowbeam. One relay for lowbeams, one relay for highbeams.

I've got a single relay setup on my zed powering driving lights, I'll make a basic video explaining how to set up a pair of relays for headlights.

that would be great! and like i said

black dragon auto sells heavy duty wiring harnesses for 30$

i have a quick headlight question…i changed my headlights then i noted the left one was not working so i put the old one back in and it still was not working…so then i figured it might be the harness so i wired up a new one and still nothing… :-( any ideas what might be going on??

the little leprechaun in your headlight switch fell asleep.

does anyone know if that harness from blackdragon is for one or both headlights? it is on page with all the other lights

so its my headlight switch?