Polarity and V-LEDS

Posted: November 11, 2010 in Trouble Shooting
Tags: , , , , , ,

I’m sure you already know that LEDs are polarity sensitive. If you didn’t know this basically means that they will not light up if the power and ground are connected backwards. So if you plug in you new V-LEDS and they do not light up, try flipping them around and plugging them back in and they should work. I want to go over some other polarity issues where flipping the connection over will not work.

Here is the classic example. Your car, truck, or motorcycle uses an 1156 style bulb and you have replaced your blinker or brake light and it won’t light up. The filament bulb that was installed before worked just fine, why is the LED not working? Simple answer is polarity. The problem here is that you can’t just flip this bulb around to make it work. The metal base is the main contact and there is a center pin in the bottom of the socket that is the other contact. The problem here is associated with the wiring on your car. The wires going to the socket are backwards. The industry standard is the metal base is the ground connection and the center pin is the power connection. Some car makers do it differently and use the metal base as the power connection and center pin as the ground connection. Why? Not too sure but it is easily fixable if you have some tools. You will simply need to cut the 2 wires routed to the plug and reconnect them backwards. Solder and heat-shrink the connections if you have the a soldering iron, otherwise a simple, crimpable, butt connector will do the trick. I have found on some cars this is not possible, usually European cars with one piece buss bar socket setups like the picture shown. You cannot modify the wiring for these sockets as all the bulbs share a common ground wire or common power supply. If you find that your car has this type of tail light assembly I highly recommend testing it with a test light to see if it is wired backwards before you purchase any LEDs.

Another polarity issue that can be a problem is on some blinker circuits. Known vehicles are the newer Jeep Grand Cherokee and Wrangler and some GM trucks and SUVs. These vehicles have a 194 sidemarker bulb that also acts like a blinker. When the parking lights are in the OFF position this bulb is off. Once you turn on your turn signals this bulb flashes on alternately of the front blinker. When the parking lights are in the ON position this bulb is on. Once you turn on your turn signals this bulb flashes off alternately of the front blinker. This is a series circuit that is fed power from 2 sides. It requires that voltage and ground be able to flow both directions through the filament of the 194 bulb. Once you replace this bulb with an LED the power cannot flow through and will cause the blinker to stop working. We have some 194 LEDs with special circuitry that will work for this application, but they are Flank style LEDs and usually do not work for this light housing application (light is shining the wrong direction).

So if you find that you are experiencing one of these problems grab a test light and test your sockets. Or put the filament bulb back in and see if everything is working.

Thanks for reading. Feel free to leave a comment or ask questions. You can leave them here or email them to me directly here: tech@v-leds.com

James the tech@v-leds.com

Comments
  1. VICTOR RIVERA says:

    I WAS READING THIS ARTICLE AND IM NOT SURE IF IT APPLIES TO MY PROBLEM. PROBABLY DOES AND JUST DONT KNOW IT.
    ANYWAYS I PURCHASE A PAIR OF THESE TYPE 2 TURN SIGNALS AND INSTALLED THEM ONTO MY AUDI. I HAD TO MODIFY THE SOCKETS FOR THESE BECAUSE THE ORIGINAL SOCKETS WERE THE ONE PRONG TYPE. SO I INSTALLED THE TWO PRONG TO MATCH THE BULBS AND THE YELLOW BLINKERS WORK WHEN OPERATED, BUT WHEN I TURN ON THE HEADLIGHTS THE WHITE LIGHT OF THE BLINKERS DON’T COME ON AT ALL. JUST WONDERING WHY IS THIS AND I’M HOPING YOU CAN SHED SOME LIGHT ON THE SITUATION.
    THANKS VERY MUCH.

  2. This could be caused by 2 things. The first thing I would need to know is if the original bulb was a parking light/blinker that used a single element bulb. Audi has used what is called a PWM (pulse width modulation) circuit for the parking/blinker lights. This means that the single element bulbs acts like a dual element bulb. It does this by using a 35 watt filament bulb, supplying only 6 volts to the bulb for parking lights and pulsing 12 volts to the bulb for the blinker. 6 Volts is not enough to turn on the white LEDs. I recommend testing the voltage of the parking light circuit to verify if you have 6 or 12 volts. If you have 12 volts than you should read this: http://wp.me/p18l5W-1D. If you need further assistance you can email me directly too, tech@v-leds.com. I am happy to help!