You finished the install, turned the key, and something is dark: a whole lamp, one side, or a single function like the DRL or the turn signal. Before assuming the lamp is bad, know this: on a new install, most "dead" lights are a connection that isn't quite made. The checks below are in order, fastest first, and the swap test near the end tells you for certain whether the problem is the lamp or the vehicle.
A lamp that is dark on the vehicle is almost always a connection problem. A fault that follows the lamp when you swap sides is the lamp. A fault that stays on the same side of the vehicle is the vehicle or its wiring.
First, name the symptom
| What you see | Most likely cause | Start here |
|---|---|---|
| One lamp completely dark, the other works | Connector, adapter harness, fuse or ground on that side | Checks 1–5, then the swap test |
| Both lamps completely dark | Power isn't reaching either side: switch position, fuse, adapter harness | Checks 3 and 4 |
| One function dead (DRL, low beam, turn, brake, reverse), the rest work | That function's pin or wire, or a vehicle setting | Checks 1–4, then the factory-lamp test |
| Comes on, then shuts off after a few seconds and stays off | The vehicle is cutting power to the circuit | "Comes on, then shuts off" below |
| Flickers, shimmers, or the turn signal blinks fast | Load or ground, not a dead lamp | Hyperflash, flicker and bulb-out warnings |
| Driving lights work, but RGB / color effects don't respond | App pairing, not the lamp | RGB Light App Setup |
| Blind-spot (BLIS) or other warning after a tail light swap | A disturbed connector, or a fitment where BLIS isn't supported | "Blind-spot warning after a tail light swap" below |
Check 1: every connector is fully seated and latched
A plug that is 90% in can light part of the lamp and leave another function dark. Push each connector until you hear or feel the click, then pull gently on the housing (not the wires) to confirm the locking tab caught.
Check every connector you touched during the install, not just the lamp's. To reach headlight bolts you may have unplugged side markers, fog lights, a horn, or a sensor; a plug left loose there shows up as a warning or a dead function that looks like the new lamp's fault.
Check 2: look at the pins
With the connector apart, look straight into both halves under a flashlight. You are looking for a pin that is bent, pushed back further than its neighbors, or corroded. A pin pushed back into the housing makes no contact even when the plug is latched.
Don't force a bent pin straight with pliers. Take a clear photo of both halves and contact us; a damaged pin on our side is covered, and we can tell from the photo which side it is.
Check 3: the adapter harness is installed
If your box included an adapter harness, it is there because your vehicle's factory plug differs from the lamp's, and the lamp will not work correctly without it. Confirm it is installed between the factory plug and the lamp, latched at both ends, and not still in the box. If you are not sure whether your install needs it, compare the factory plug to the lamp's plug: if they don't mate directly, the adapter goes in between.
Check 4: switch position and fuses
- Test with the headlight switch at ON, not AUTO. In daylight, AUTO can keep the low beams off and make a working lamp look dead.
- Check the vehicle's settings menu. On some vehicles the DRL can be turned off in settings, and some DRL systems behave differently with the parking brake set or the transmission in Park. Rule these out before suspecting the lamp.
- Check the lighting fuses. Your owner's manual lists which fuses feed the headlights, DRL, turn signals and tail lights. A fuse that blew during the install (a tool touching a live terminal is enough) will kill one function on one or both sides.
Check 5: the ground
A ground through paint, undercoating or a corroded terminal can leave a lamp dark, dim, or working on one function and not another. Remove it, clean to bare metal, and retighten. The hyperflash and flicker guide covers grounds in more detail.
The swap test: lamp or vehicle?
If one side is dark and the other works, this one test settles it.
- Unplug both lamps.
- Plug the working lamp into the dark side's connector. You don't need to mount it; if the harness reaches, let the lamp hang supported while you test.
- Turn the lights on.
Then read the result:
- The working lamp lights on the dark side: the vehicle side is fine and the problem is the lamp you removed. That is what the warranty is for; see "Still dark" below.
- The working lamp is now dark too: the lamp is fine. Power isn't reaching that connector, so the cause is the vehicle side: a fuse, a damaged factory plug, the adapter harness, or the wiring. Not sure how to trace it? Ask our install team and tell them the swap-test result.
Write down the result. It is the single most useful thing you can tell us.
The factory-lamp test: is the vehicle sending power?
If one function is dead on both sides (for example, no DRL on either lamp), plug the original factory lamp back in for a minute and check that function. If the factory lamp doesn't light on that function either, the vehicle isn't sending the signal (a setting, a fuse, or a vehicle fault), and no replacement lamp will change it.
Comes on, then shuts off and stays off
This is a different problem from flicker, and worth separating clearly. If a lamp lights normally, then within a few seconds or minutes goes out and stays out until you restart the vehicle, the vehicle's computer is cutting power to that circuit. Some trucks monitor their lighting circuits closely; when they read the LED's low draw as a failed bulb, they shut the circuit down to protect it.
Don't add parts to fix this on your own; a resistor sized for hyperflash may not be the right fix here. Record a video from a cold start: lights on, keep filming for at least 60 seconds until the lamp shuts off, and include the dash. Send it with your vehicle's year, model and trim. This is a vehicle-specific case, and the video tells us exactly what is happening.
Blind-spot warning after a tail light swap
Where your truck's blind-spot (BLIS) hardware lives decides what to expect:
- Sensor in the bumper: replacing the tail lights doesn't involve the BLIS system. A BLIS warning that appears after install almost always means a connector near the bumper or tail light was disturbed during the work. Re-seat everything you unplugged.
- BLIS components in the tail light area: the product page's Compatibility section states whether your RIGNOX tail lights retain BLIS on your trim. If it says BLIS is retained and you see a warning, re-seat the connectors and contact us with a photo of the dash. If the page says your BLIS configuration is not supported, the warning is expected with that product.
Things not to do
- Don't cut or splice the factory wiring to make a lamp work. RIGNOX lamps are plug-and-play; if a plug doesn't fit, something is wrong and we want to know. Damage from cut or spliced wiring isn't covered by the warranty.
- Don't open the housing. An opened lamp can't be assessed and is no longer sealed.
- Don't grease the connectors unless your installation guide says to. Grease in a sealed connector can cause exactly the contact problems you are trying to fix.
Still dark: start a warranty claim
If the checks are done and the swap test says the lamp is the problem, start a warranty claim. Every RIGNOX support case starts with photos and video, because a lamp can't be diagnosed from a description. Have these ready:
- A video of each function with the engine running: low beam, high beam, DRL, left and right turn (use the stalk, not the hazards), and for tail lights, brake and reverse with a helper. 15 to 30 seconds is enough.
- The result of the swap test, and whether the factory lamp worked on that function.
- A photo of each connector, both halves, pins visible.
- A photo of the label on the back of the lamp.
- Your order number, and your vehicle's year, make, model and trim.
With that we can usually tell you within two business days whether you need a part, a reseat, or a replacement, and in most cases you won't need to send the old lamp back unless we ask for it. Past the 2-year warranty? Contact us anyway: we'll still help you troubleshoot, free.
The swap test pointed at the vehicle side, or you couldn't do it? That's an install question, not a claim: ask our install team with the same photos and videos.
The short version
- Most dead lights on a new install are a connection: re-seat and latch every connector you touched, check the pins, and make sure the adapter harness (if included) is installed.
- Test with the headlight switch at ON, check the settings menu and the fuses.
- Swap the working lamp to the dark side. If the fault follows the lamp, it's the lamp (warranty claim); if it stays, it's the vehicle or wiring (installation help).
- A lamp that lights then shuts off and stays off is the vehicle cutting the circuit. Film 60 seconds from a cold start and send it to us.
- Don't cut wiring, open the housing, or grease connectors.
- Still dark: start a warranty claim with videos of each function, the swap-test result, connector photos and the back label.
Your vehicle's connector and mounting steps are in the RIGNOX installation guides.
