Finally figured out 4th JDM One Piece Headlight Conversion with USDM Harness!!

[Freakin'H22A]

YESSSSSSSSS!!!!!!!! :w00t Finally Solved the Riddle for 4th Gen JDM Headlights using Stock Harness and this is for real guys!!!!!!

I'm glad to share this with you on how to wire our 4th Gen JDM Headlights using the Stock Harness and no relays or additional wires needed. Well actually, you may want to buy the silicone plugs which won't melt when the conversion of higher Wattage bulbs are replaced. This was kind of tricky, but they work without a problem stock as they can be :clap

USDM HEADLIGHT WIRING DIAGRAM



For starters I have to say that "City Lights" H1 bulbs are very bright and should be used as a separate switch, could be combined with fog lights. This mentioned, let's concentrate on the H4 bulbs.

The trick here is to know the arrangment of the H4's since they have only 3 wires (GND, HIGH BEAM, LOW BEAM). The problem here is that our stock harness (USDM) have two cables per plug and not three as mentioned above. It was practically overwelming when thinking on how to do this conversion; however, the trick was to know that the H4's don't have polarity. Either forward or reversed electric flow can be arranged.

No more going around the bush!!!

First thing you need to know is that the car's electrical system is based on Grounding (negative electron flow) over the chasis. In other words, the battery's Positive is always connected, 90% of all switches (Ground Terminal) when closed it completes the circuit permiting the positive (+) flow of electricity.

Secondly, you need to look at the diagram above and pay attention to this:
***note: I colored matched them so you can identify the ones that have the same electric purpose.

Stock Left Headlight:

Low Beam (Blk) - GROUND
Low Beam (Red/Yel) - POSITIVE CHARGE
High Beam (Red/Yel) - POSITIVE CHARGE
High Beam (Red/Blu) - GROUND TERMINAL WHEN DIMMER RELAY/COMBINATION SWITCH IS ACTIVATED

Stock Right Headlight:

Low Beam (Blk) - GROUND
Low Beam (Red/Grn) - POSITIVE CHARGE
High Beam (Red/ Grn) - POSITIVE CHARGE
High Beam (Red/Blu) - GROUND TERMINAL WHEN DIMMER RELAY/COMBINATION SWITCH IS ACTIVATED

Now that we have these identified, let's concentrate on the Left Headlight H4 bulb. You can see that on the H4 connector we have one common ground for both High Beam and Low Beams; therefore, taking a closer look at the Left Headlight diagram we see that we have one common power source (Low/High (Red/Yel)). This said, man I can't help smiling , by connecting both Low/High (Red/Yel) wires together and soldering it to the negative connector on the H4 it will give you the a common Power Source to both High/Low beams just like the diagram. Finally, the Low Beam (Blk) is connected to the Low Beam H4 connector and the High Beam (Red/Blu) is connected to the High Beam H4 connector.

RIGHT SIDE HEADLIGHT IS VICE VERSA - instead of Low/High (Red/Yel) wires you use the Low/High (Red/GRN) wires.

This gives you the exact diagram above.

***theory of functionality: The Combination Light Switch when turned on (position in diagram) the switch permits ground point to be closed and low beam to ignite; therefore, permiting only electricity to Low Beam (Blk) - GROUND as well as Low Beam (Red/Yel) - POSITIVE CHARGE. Similarly, when Combination Light Switch is rotated to High Beam position High Beam (Red/Blu) ground is closed permiting then electric flow to the High Beam.

[johnlude85]

great man. this will defenately help me a whole bunch when i do mine.

is there already a "how to" for this mods. if not i think we should make it one.

[Freakin'H22A]

Originally Posted by johnlude85

great man. this will defenately help me a whole bunch when i do mine.

is there already a "how to" for this mods. if not i think we should make it one.

No problem dude, SHO has helped me a lot and I liked to share some of my knowledge. Well, all the procedure is detailed there... so is up to Blake or an administrator to put this on the FAQ.

[98vtec]

placing in FAQ as we speak...thanks

[DrivinVtec]

i dont on a 4th gen but sure is some good info. good job

[Sodikai]

Wow great! Good stuff in this thread, thanks!
I already deleted one post for asking a stupid question, but check me on this. After reading and studying the diagram, the way you have it set up, both positive and negative lines (red/yel and red/grn) go through the H4 bulb which is in the old usdm "low beam" position. This leaves the usdm "high beam" position unwired correct? That is the city bulb as you call it, the H1. So if I wanted to have it operational I would need to wire it up seperately? I've had my lights boxed up for so long I don't remember which slot is H1 and which is H4 so maybe I have the "low" and "high" slots reversed. But it makes sense that the H4 would be the usdm "low" beam outter position. Forgive me if I'm being dense, but if so my shame will live on in the FAQ for all to mock and scorn.
Thanks again!

[Freakin'H22A]

Originally Posted by Sodikai

Wow great! Good stuff in this thread, thanks!
I already deleted one post for asking a stupid question, but check me on this. After reading and studying the diagram, the way you have it set up, both positive and negative lines (red/yel and red/grn) go through the H4 bulb which is in the old usdm "low beam" position. This leaves the usdm "high beam" position unwired correct?

Ok, for one H4 bulbs are both High and Low Beams in one bulb. It replaces the need of two bulbs to do the work. Red/Yel and Red/Green are not both positive and negative, you may be misunderstanding the instructions. No worries Take a good look at the diagram again, for the left Headlight you have one common power wire which is the Red/Yel... same thing for the Right Headlight except in this case is Red/Grn. The H4 has three cables as mentioned above, High Beam, Low Beam, and ground. This bulb has a common ground for both beams so you need to work it all the way around and make the ground be the common power source for both beams and instead of a power signal to connect the High/Low beams you have left both stock grounds Low Beam's BLK as well as High Beam's Red/Blu. If you look closely to the diagram, you will see that the Red/Yel and Red/Green are both common and the Red/Blu and Blk are the lights ground. Hope you understood this time.

Originally Posted by Sodikai

That is the city bulb as you call it, the H1. So if I wanted to have it operational I would need to wire it up seperately? I've had my lights boxed up for so long I don't remember which slot is H1 and which is H4 so maybe I have the "low" and "high" slots reversed. But it makes sense that the H4 would be the usdm "low" beam outter position. Forgive me if I'm being dense, but if so my shame will live on in the FAQ for all to mock and scorn.
Thanks again!

Dude!!!!! don't be hard on yourself... this wasn't easy. I worked with my friend which is an Electrical Engineer and myself a Mechanical Engineer and it took us an our to figure this out. Don't worry about it. Simple man... just disconnect all your wires leaving the stock untouched, follow the instructions above and about the H1 bulbs is a good thing to connect them separately for two reasons, they are too damn bright and you don't want cops harrassing your ass and two there are not stock wires left for you to connect. And where you seem to be confused is at thinking that the H4 is one beam and the H1 is another; when the H4 bulb are both beams selected as stock and H1 are always turned on without turning on the lights in Japan.

Take care and hope you figure it out by now.

Originally Posted by 98vtec

placing in FAQ as we speak...thanks

[904lude]

ok just to clear a few things up... when looking at the jdm bulbs backing or clip for that matter... (my wires were gone when i bought it but i do have the clip) which metal prong is which (in your usdm wire conversion) im pretty sure they come from japan with the black ground wire on the top horizontal prong and the red/green (pass headlight) wire goes on the left vertical prong, but what goes on the right vertical prong? the only reason im confused is because i have the clip that connects to the bulb but there is no wire coming from them... can you please clarify, it would be greatly appreciated. i just wanna know which wire goes on the horizontal prong and which wires go on the two vertical prongs (left and right if it matters).

also just curious, how did everyone end up wiring the city lights? they are the inner ones correct? when do you guys actually ever run them? i thought about running them so they come on with my corner lights but i dont wanna piss people off if they are really that bright! IMO i say screw others on the road, let them be blinded by the jdm goodness LOL jk.

Thanks a mill guys for any clarifications! :clap

[Freakin'H22A]

Originally Posted by 904lude

ok just to clear a few things up... when looking at the jdm bulbs backing or clip for that matter... (my wires were gone when i bought it but i do have the clip) which metal prong is which (in your usdm wire conversion) im pretty sure they come from japan with the black ground wire on the top horizontal prong and the red/green (pass headlight) wire goes on the left vertical prong, but what goes on the right vertical prong? the only reason im confused is because i have the clip that connects to the bulb but there is no wire coming from them... can you please clarify, it would be greatly appreciated. i just wanna know which wire goes on the horizontal prong and which wires go on the two vertical prongs (left and right if it matters).

also just curious, how did everyone end up wiring the city lights? they are the inner ones correct? when do you guys actually ever run them? i thought about running them so they come on with my corner lights but i dont wanna piss people off if they are really that bright! IMO i say screw others on the road, let them be blinded by the jdm goodness LOL jk.

Thanks a mill guys for any clarifications! :clap

Go to AutoZone and get some H4 Plugs it prevents plugs to overheat and also, you don't have to worry about the wires. What you need to consider is to match the cables as this simple google search shows:

http://homepage.ntlworld.com/jim_has...161941165a.jpg

About the city lights, I made a separate connection in conjunction with the PIAA fog lights... they turn on by a switch. I'll use my city lights on afternoons, and foggy rainy days.... or just to piss someone off

[DJ NaChO hO]

I'm a little confused, some places say the prelude hid lights are h1 and h4 and some say 9005 and 9006. Which one is it? And aren't JDM HIDs thinner then USDM HID bulbs?

[Freakin'H22A]

Originally Posted by DJ NaChO hO

I'm a little confused, some places say the prelude hid lights are h1 and h4 and some say 9005 and 9006. Which one is it? And aren't JDM HIDs thinner then USDM HID bulbs?

9000's are for the color of it... whitter or bluer

[904lude]

so im currently sitting in my garage after attempting to wire my H4 bulbs... i wired it like you said w/ the powers going to the ground. so before actually installing the light i attached the bulb to the clip and tested it out, to make sure both high and low beams worked... well the bulb started to smoke when i turned it on????? what did i do wrong???

to clarify... when looking at an H4 bulb one of the filaments has a sheild around it and the other doesnt... is the low beam the one w/ the sheild around it or vise versa?

sorry for making somethin so easy difficult, thanks again for the help!

EDIT: found out the smoking was from using the old bulb which i guess i touched and was burning the oil from my fingers... i tried out the new bulb (used gloves) and no smoke!!!!

i would still like to make sure i have the high as the high and the low as the low though... id hate to be running the highs all the time by mistake!

[Freakin'H22A]

Originally Posted by 904lude

so im currently sitting in my garage after attempting to wire my H4 bulbs... i wired it like you said w/ the powers going to the ground. so before actually installing the light i attached the bulb to the clip and tested it out, to make sure both high and low beams worked... well the bulb started to smoke when i turned it on????? what did i do wrong???

to clarify... when looking at an H4 bulb one of the filaments has a sheild around it and the other doesnt... is the low beam the one w/ the sheild around it or vise versa?

sorry for making somethin so easy difficult, thanks again for the help!

EDIT: found out the smoking was from using the old bulb which i guess i touched and was burning the oil from my fingers... i tried out the new bulb (used gloves) and no smoke!!!!

i would still like to make sure i have the high as the high and the low as the low though... id hate to be running the highs all the time by mistake!

This can be done very easily. Get yourself 3 wires and strip all ends. Since you want to make sure which one is your High & Low on the bulb. Attach 1 wire to each connector, then stand in front of the battery and the negative connector on the wire attached to the bulb connector place it on the Positive (+) terminal of the battery. Then to figure out (or making sure) which one is High or Low, just plug either one of the other 2 wires left to the negative of the battery (is the same methodology used for the wiring I explained earlier but you're doing it directly). Once you do this with the 2nd wire and the bulb lit up, make sure you do the same for the other wire you left hanging.... remember leave the Positive (+) terminal always attached ... you will notice that the highest beam will obviously be more intensive than the low... make sure when the plug is wired to have the same arrangement as the one you just found out.

P.S.

I would recommend to wipe clean with a soft cloth every residue on the bulb.

[904lude]

thanks everyone for the help! i finally got it done... it was well worth it! +10pts to all who helped! next ill be hitting up the H1's to a switch... and then putting my yellow fogs and fender markers on!!! :clap

[Freakin'H22A]

Originally Posted by 904lude

thanks everyone for the help! i finally got it done... it was well worth it! +10pts to all who helped! next ill be hitting up the H1's to a switch... and then putting my yellow fogs and fender markers on!!! :clap

no problem