#20. I’ve replaced my tail lights with LED units and they don’t work right. What’s wrong?
Wow! What a loaded question. There are so many different things that could be wrong. Some issues have similar signs while others are distinct. Let’s hit the most common stuff.
Symptom #1: Both turn signals flicker or seem dull and don’t flash, but they work fine when the 4-way hazards are turned on (maybe).
Common Cause; LED lights use very little amperage to give you lots of light. However, the regular metal “can” flasher (#552 for instance) lives by amperage. With the 4-ways on, there is enough amperage going through the flasher to make it work but either turn signal alone is too little amperage. Cure this by (a) getting an electronic flasher that is intended for LED lights [this is often a more expensive answer] or (b) add a dummy load to each side - left and right - to increase the amperage flow and make the flasher work.
Symptom #2: One side works and the other side doesn’t (or is not as bright).
Common Cause: If one side of identical circuits doesn’t work, there’s something wrong with that side. Check the ground(s), “bench test” each light to make sure they are fine, and most helpful - take voltage readings at each light and elsewhere in the system as needed. We have been finding that with some wiring panels there is unwanted resistance in the panel connections that can create a voltage drop, frequently to just one of the tail lights. And since LED’s can be sensitive to low voltage, this is a likely problem. There should be a full 12 volts all the way to the back of the vehicle and both sides should be the same.
Symptom #3: The LED lights seem fine when viewed up close but as you get farther away they are quite dim.
Common Cause: LED’s are very directional and need to point straight backwards from the vehicle. If you have put an LED bulb replacement into an existing light housing, and if that housing is on an angle, you’re not going to be pleased with the LED at a distance. For build-in and flush mount lights, the directions should explain this. There is a little bit of diffusion off center, but the best and brightest light is “straight on” to an LED.
Symptom #4: I have three different feed wires for each light on my car but the LED light only has two wires plus the ground. What’s up?
Common Cause: You’ve kind of gotten the cart before the horse in-that you have bought a light that doesn’t match your vehicle’s system. Your three different wires are for (1) the taillight, (2) the brake light, and (3) the turn signal as a separate light from the brake light (probably amber in your original vehicle). The LED taillight has been designed (as most of them are) for a vehicle with combined brake/ turn light. But those vehicles that have combined brake/turn also have designed in what is called brake light override - that is, it prevents the brake light from “overriding” the turn signal (and blocking it out) when the turn signal on one side is active. Again, the good news in that there are additional parts that will marry the light to your system and make it work perfectly. StreetWorks also has build-in, flush mount LED taillights specifically for those vehicles with separate brake and turn signal lights.
(More next time on Brake Light Override.)
Steve Watson, Watson's StreetWorks, http://www.watsons-streetworks.com
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