Patrick - LED Taillight problems

[Xack]

Originally Posted by DanEC

Everything checks out. Bulbs light up in the light fixture using my battery charger. I reinstalled in my car and with my test light I show power at the connection but the bulb doesn't light. I checked polarity with a standard 1157 and they are the same. Only thought is that voltage off of battery is not sufficient to energize the LEDs on the tail light circuit - so next I'm going to wheel the car out and start it up and see if running voltage will light the tail light circuit.

If that doesn't work then I'll call superbightled since they haven't answered my email yet.

Edit - when I said polarity that was a misnomer. What I checked was orientation of the two illumination circuits and compared to a standard 1157 bulb.

What is your steady-state battery voltage? If you do not have 12-13 volts at the bulb, there is a resistance probably at the switch or between there and the bulb(s). Disconnect the battery and Check resistance on the LOW resistance setting on your VOM. Measure resistance between the bulb ground on the connector to the battery negative terminal. Also measure resistance between the bulb power and the connector on the load side of the light switch. Any resistance here will drop your voltage to the bulb(s). You should not see more than 1 or 2 OHMS of resistance in your wiring. LED's are voltage sensitive, meaning they will not light up if the source voltage is too low. They sink relatively low current compared to incandescent type bulbs. Incandescent bulbs (current sensitive) will turn on if they can sink enough current to glow the filament, even if source power voltage is low like 9 volts or so.

You can also run a wire from the battery ground and attach it to your bulb ground to see if you have a grounding problem. (I suspect a poor ground circuit) If you don't see improvement, the problem is on the power side, meaning you have a poor connection on the switch or any connection between the switch and the bulb filament(s). Check voltage at the fuse, switch, and all connections all the way to the bulb to see if you are getting anything but the same voltage measured at your battery (terminal to terminal).