Our tail lights are reverse polarity?

[Red]

So I thought I'd treat my car to LED tail/brake lights as a safety update, since they're supposed to light up a little faster and give the guy behind me more time to stop instead of hitting me.

Found a place called CarID.com, seemed competitive, and ordered some LUMEN® 1157CR bulbs. I used to know how to change a light bulb...and although I know are HEADlights are reverse polarity (switched ground instead of switched hot) never heard anything about the tail lights being backwards. And these even have load resistors built in, so there's no problem with fast flashing or needing a new flasher.

Yeah...the bulbs won't light up at all, the polarity in the tail light sockets apparently is reverse from the rest of the world. The bulbs want the outer socket hot "like God and Henry Ford intended" and ground applied to the base contacts to turn each filament on. Just like the headlights. The car is wired up backwards. I could cut and splice but I really don't want to do that to the harness. I didn't have a voltmeter with me in the car, but it seems pretty certain and obvious, the left hand of Toyota struck again. Our electrics were designed by Lucas alumni, I guess.

Anyone know if there are any commercial LED bulbs that will work in our oddball old cars?

[MisterJerk]

I do not think you will need to cut and splice. Couldn't the wires be de-pinned at the plug and switched around? I would love to see these work and the final result.

[gotzoom?]

Kouki cars reverse polarity, but zenki do not. You'll need to add a diode to your circuit to stop the short. a 1/2 watt diode should be enough. Test with a multimeter and you'll see what is happening. It's a simple problem to fix.

[Red]

I don't see what you guys are talking about.

Adding a diode? To what and where? Adding a diode won't change the polarity in either circuit.

There are two circuits (tail and brake) involved and that means a simple wire swap at the bulb isn't going to do it, the circuits have to be modified. I don't recall ever seeing the 85/87 models shown with different tail wiring in the manuals, but my wiring manual IS an 85 so of course it only shows things one way.<G> Can you tell me what the change is supposed to be, specifically??

There's probably a way to change the wiring at the brake relay that would fix things, along with another swap in the marker/tail light lines, but that would also be setting up a problem down the line if anyone ever needed to touch the lights and rashly assumed the car was wired the way they're supposed to be wired.

Superbrightleds has some unpolarized 1157 bulbs, but they're less than 1/2 as bright as the better ones.

If I can't "fix it right" and clean, I'll hold out for better bulbs or do something old school style, like build my own.

[gotzoom?]

On a kouki car, when the brake pedal is not depressed, the + brake wire is grounded. If you're using that to make the LEDs increase brightness, you need to put a diode in series on that circuit otherwise the circuit shorts and all your LEDs go out. A diode is like a one-way valve that will prevent the circuit from grounding when the pedal is not pressed. The line on the diode indicates the "output" side of the diode. Remember that electricity travels from negative to positive direction. If you design your circuit correctly, there is no need to change any of the car's wiring. I troubleshot this for a buddy and adding diodes on each circuit of LEDs resolved the problem. If this still makes no sense, you should do more research on basic electronics. If you do things wrong, you can create a dangerous situation with shorts or overloaded wiring that can cause a fire.

[Red]

Funny thing, the 1985 EWD (electrical wiring diagrams book) is WRONG FOR THE CAR. It shows separate 1156 single filament bulbs for the brake and tail lights, so I'm on my own.

zoom, we're loosing something in translation here. You say " when the brake pedal is not depressed, the + brake wire is grounded." except, when you ground a + wire you create a short and blow a fuse, unless there's a load in the circuit. And when the brake pedal is not depresed--there's no load, no circuit made. I know what a diode is, and it will not make any difference in how the brake circuit works. There are two separate circuits to the 1157 bulbs. Turning on the tail lights powers one filament, stepping on the brakes powers a second separate filament. All they have in common should be the one common ground point, in the back of the car. Anything you can do with a diode in the ront of the car will not affect that.

And you don't change the brightness of the LEDs to "make" the brake light. Not at all. You turn on more/different LEDs, you don't change anything about the brightness of individual LEDs in any conventional 1157 replacement. You're getting these confused with something else.

Like the SOB who wrote the 1985 EWD for the wrong circuit entirely. Or the other SOB who designed the wiring in the car, ignoring the world-wide conventions of switched hot and common ground. It's just wrong for this application.

[assassin10000]

Normal AFAIK. I run LED's I got somewhere years ago. Plugged right in and worked.

Brake switch put's 12v to one side of the bulb.
Headlight switch triggers a relay which put's power to the other side.
Bulb is constantly grounded through the housing.

Same for both kouki and zenki.

Andrew

[ga_goosh]

red you can arange 4 diodes in a way that the polarity wont mater. it will keep you from cutting your harness especially if you put this on the pcb before the LEDs

[rongfk]

i have an 85 zeinki gts that i built led tail lights for. this would explain why i had some issues. now that ive redone my leds and replaced the resistors to what i thought was the correct ones, this make me wonder if it even going to work after all my efforts. many, many hours into these damn things..sorry for this, just searching for answers.

[Markevans!]

So I thought I'd treat my car to LED tail/brake lights as a safety update, since they're supposed to light up a little faster and give the guy behind me more time to stop instead of hitting me.

Found a place called CarID.com, seemed competitive, and ordered some LUMEN® 1157CR bulbs. I used to know how to change a light bulb...and although I know are HEADlights are reverse polarity (switched ground instead of switched hot) never heard anything about the tail lights being backwards. And these even have load resistors built in, so there's no problem with fast flashing or needing a new flasher.

Yeah...the bulbs won't light up at all, the polarity in the tail light sockets apparently is reverse from the rest of the world. The bulbs want the outer socket hot "like God and Henry Ford intended" and ground applied to the base led bulb contacts to turn each filament on. Just like the headlights. The car is wired up backwards. I could cut and splice but I really don't want to do that to the harness. I didn't have a voltmeter with me in the car, but it seems pretty certain and obvious, the left hand of Toyota struck again. Our electrics were designed by Lucas alumni, I guess.

Anyone know if there are any commercial LED bulbs that will work in our oddball old cars?

I have never faced such problems with my led lights but I will search good led bulbs for you. Give me some time.