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If your LED module does not produce any light when powered on, the problem is almost always a wiring or connection issue — not a dead LED. Work through this checklist from most common to least common cause before assuming the module is defective.
Checklist
1. Reverse polarity
The most common cause. LEDs are diodes — they only conduct current in one direction. If the positive and negative leads are swapped, the LED simply will not light. Reversing polarity at normal operating current will not damage the LED.
Fix: Swap the output leads from the driver to the LED module. Check the module’s solder pad markings for + and -.
2. No connection or loose wires
A wire that looks connected may not be making electrical contact — cold solder joints, loose screw terminals, or a wire strand touching the wrong pad.
Check: Gently tug each wire connection. Inspect solder joints for a shiny, wetted appearance. Check screw terminals are tight.
Fix: Reflow solder joints. Re-strip and re-terminate wires. Tighten terminals.
3. Driver has no input power
The driver itself may not be receiving power. Check the input side, not just the output.
Check: Measure voltage at the driver’s input terminals with a multimeter. Is the supply turned on? Is the fuse intact?
Fix: Trace the power path from supply to driver. Fix the break.
4. Input voltage below driver minimum
If the supply voltage is below the driver’s minimum input threshold, the driver will not start. There is no error indicator — it simply produces no output.
Check: Measure supply voltage under load. Compare to the driver’s minimum: (Vf × LEDs) + overhead (2.0V PowerPuck, 2.5V BuckPuck).
Fix: Increase supply voltage or reduce the number of series LEDs.
5. Dimming signal at zero
If you are using an externally dimmable driver, the dimming input may be set to zero (fully off). A disconnected dimming pot on some driver models defaults to off rather than full brightness.
Check: Disconnect the dimming signal. Most externally dimmable drivers default to full output when the dimming input is disconnected — if the LED lights up, the dimming signal was the problem.
Fix: Adjust the dimming pot or signal to a non-zero value. Check the driver’s datasheet for the default behavior when the dimming input is open.
6. Dead LED (rare)
LED failure does happen but is uncommon. In a multi-LED series module (Tri-Star, Quad, 7-Up), a single dead LED breaks the entire series circuit — none of the LEDs will light.
Check: Measure the resistance across the LED module’s pads with a multimeter. An open circuit (infinite resistance in both directions) suggests a dead LED or broken trace. A healthy LED will show low resistance in one direction and high in the other (diode behavior).
Fix: If the module is defective, contact us for a replacement.
