You bolted in a new set of LED lights, hit the turn signal, and it's blinking twice as fast as it used to. Or the dash says a bulb is out when every light is clearly on. Or the DRL has a faint shimmer at idle that wasn't there before. These three symptoms get lumped together on forums, but they are two different problems with different fixes, and knowing which one you have is most of the job.
Hyperflash and bulb-out warnings are a current problem: the vehicle sees too little load and assumes a bulb died. Flicker is a signal problem: the vehicle is pulsing the circuit and the LED is showing the pulses. Load fixes the first. Filtering fixes the second.
Why a car cares how much current a light draws
Every vehicle built in the last few decades checks its own bulbs. On older cars the flasher relay does it mechanically: a halogen turn-signal bulb draws around 21 to 27 watts, and if the current through the relay drops (because a filament broke), the relay's timing changes and the signal blinks fast. That is where hyperflash comes from; it was designed as a warning.
On newer cars the body control module (BCM) does the same check electronically, on every lighting circuit, and reports the result on the dash as a bulb-out message. Some vehicles also send brief diagnostic pulses down each circuit when the lamp is off, to confirm a bulb is still connected.
A full-LED assembly draws a fraction of the current of the bulbs it replaces. The lamp is working perfectly; the vehicle just can't tell, because it was calibrated for a filament.
What RIGNOX builds in, and why a few vehicles still need more
Every RIGNOX headlight and tail light ships with CANbus decoders built into the assembly. They present enough electrical load and smooth enough of the vehicle's pulses that, on most vehicles, the lamp plugs into the factory harness and the dash stays quiet. That covers the large majority of installs, and it is why the box does not contain a separate decoder or resistor: most owners would never use it.
A small number of vehicles check the turn-signal circuit more aggressively than the built-in decoder is sized for, and which ones depends on year, trim and sometimes the individual vehicle's software, not just the model. If yours hyperflashes after install, that is not a fault in the lamp; it is a vehicle that wants closer to the full filament load. Contact us with your vehicle details and order number and we will send you the correct load resistor. We keep them for exactly this situation rather than shipping one in every box.
Connectors are a different matter and are handled before the box ships. Where a vehicle uses a factory lighting plug that differs from the lamp's, the matching adapter harness is included, so the install stays plug-and-play with nothing cut. You don't need to ask for it.
One more thing to know before you plan the build: if you replace headlights and tail lights together, the turn-signal circuit on each side loses the front and rear filament at once. The total load per side drops further than a single swap, and some vehicles monitor front and rear separately. A resistor that was enough for tail lights alone may not be enough once the front goes LED too; you may need a higher-wattage resistor, or one at each end. When you contact us, tell us both products are on the same vehicle and we will spec it for that, not for one lamp at a time.
Symptom 1: turn signals blink fast (hyperflash)
Cause: low current on the turn-signal circuit. Fix: add load.
Before touching anything, do the one test that actually isolates the problem: use the turn signal stalk, not the hazards. On most vehicles hazards run through a different path and will not hyperflash even when the turn signals do, so "hazards look fine" tells you nothing. Signal left, then right, and note whether one side or both is fast.
- Both sides fast, immediately after install: the vehicle needs an external resistor on each turn circuit. Contact us and we'll send them.
- One side fast: that side's harness plug isn't fully seated, or if a resistor is already installed, it isn't making contact. Re-seat the connector first; it is the most common cause and takes ten seconds.
- Fast only after both front and rear went LED: the resistor is undersized for the combined circuit. See above.
- Older vehicle with a plug-in flasher relay: an LED-compatible electronic flasher relay fixes the rate without resistors and without heat. It does not clear a bulb-out message if the vehicle also has one; for that you still need load.
If you are installing a resistor: it goes in parallel across the turn-signal positive and ground on that side, and it must be mounted on bare metal, away from plastic and wiring. A 50-watt resistor gets hot enough to melt a loom. Mount it on the frame or a bracket, never zip-tied to the harness.
Symptom 2: dash says a bulb is out
Cause: same as hyperflash; the BCM is reporting the low load instead of, or in addition to, blinking fast. Fix: add load, then clear the stored fault.
Two things people miss here:
- The message may be stale. On many vehicles the fault stays displayed until the BCM re-checks, which can be a few key cycles or a drive. After adding a resistor, cycle the ignition several times and drive before deciding it didn't work.
- Some vehicles need a reset. If the load is correct and the message persists, disconnect the negative battery terminal for 30 minutes and reconnect. This clears the BCM's stored bulb state on a number of platforms and is the first thing several lighting manufacturers tell their own customers to try.
If the message names a lamp that is not the one you replaced, check whether the harness routing disturbed a neighboring connector during the install. It happens more than you'd think.
Symptom 3: DRL or running light flickers, shimmers, or pulses
Cause: the vehicle is driving that circuit with a pulsed (PWM) signal, usually to dim the DRL when the headlights come on, and the LED is fast enough to show the pulses. A halogen filament is too slow to flicker; an LED isn't. Fix: filtering, not load.
This is the symptom where forum advice does the most damage, because people add a load resistor and it doesn't help. A resistor changes how much current flows; it does nothing to smooth a pulsed signal. The built-in decoder in RIGNOX assemblies includes the capacitance for this, which is why flicker on our lamps is rare and, when it happens, almost always points to something upstream:
- Weak ground. The number one cause of intermittent LED behavior of any kind. A ground bolted through paint, undercoating, or a corroded ring terminal will produce shimmer at idle, random dropouts, or one side behaving differently from the other. Remove the ground, clean to bare metal, retighten. Do this before anything else.
- Flicker only at idle, gone when revving. Alternator ripple on a marginal battery or ground. Check the battery terminals and the ground.
- Flicker began months after a clean install. Dealer software updates can change how aggressively the BCM checks or pulses lighting circuits. If a visit to the dealer preceded the flicker, that is the cause, and the fix is usually the reset above; if not, contact us.
- Vehicle-specific DRL logic. A few vehicles share the DRL and high-beam circuit or use unusual dimming schemes. If the ground and battery check out and it still flickers, it is a support case, not a DIY one.
The diagnosis rule. Fast blink or bulb-out message: add load (resistor, or LED flasher on older cars), re-seat connectors, then reset the BCM. Shimmer or pulse: check the ground first, then the battery, then contact us. Never add a resistor to fix flicker; it won't, and it adds heat for nothing.
Three things to check before you contact anyone
- Every connector is fully seated and latched. A plug that is 90% in will light the lamp and still cause every symptom on this page.
- The ground point is bare metal and tight. Paint and undercoating are insulators.
- You tested with the stalk, one side at a time, not the hazards.
If it's still doing it: what to send us
Every RIGNOX support case starts with photos and video, because a symptom cannot be diagnosed from a description and "it flickers" means five different things. Send:
- A video of the symptom itself: 15 to 30 seconds, engine running, showing the turn signal blinking (each side separately) or the flicker. For flicker, film at idle and then with a light rev so we can see whether it changes.
- A photo or short video of the dash showing the warning message, if there is one.
- A photo of each harness connection at the lamp, plug fully visible, and of the resistor and where it is mounted if one is installed.
- A photo of the ground point.
- Your order number, year/make/model/trim, and whether both headlights and tail lights on this vehicle are RIGNOX.
With that we can usually tell same-day whether you need a resistor, a different resistor, a reseat, or a replacement, and ship whatever is needed. Without it we have to ask for it, and that is a day lost on both sides.
The short version
- Hyperflash and bulb-out warnings mean the vehicle sees too little current. The built-in decoder covers most vehicles; a few need an external resistor, which we send on request; front-plus-rear LED needs more load than either alone.
- Flicker means the vehicle is pulsing the circuit. Fix with filtering, not load. On a RIGNOX lamp it usually points to a weak ground or a battery issue.
- Test turn signals with the stalk, one side at a time. Hazards don't hyperflash and prove nothing.
- Resistors go on bare metal, never on the loom.
- Re-seat connectors, clean the ground, reset the BCM by pulling the negative terminal for 30 minutes. Then send video, photos and your order number.
The connector and mounting steps for your specific vehicle are in the RIGNOX installation guides. If moisture inside the lens is your issue rather than electrical, that is a different problem with its own rule: normal fog or a real leak.