Okay, the high flash rate is caused by the LEDs’ extremely low current drain: they use far less electricity than the oldtech incandescent bulbs. Unfortunately, the indicator-signal relay needs the higher current to activate properly. The light flashes like a kindergartner on Red Bull because the relay is falsely sensing a burned-out bulb. If your car uses a conventional two-pin flasher relay, you can upgrade to a heavy-duty or electronic flasher relay. That’s the plug-and-play solution.

This may not be possible if you have a newfangled car with an integrated lighting module that won’t play nice with the LEDs. If this is the case, then you’ll need to add some simple wiring. We picked up the LED-specifi c ballast pictured here from a Web site that specialises in LED replacement bulbs, but you can fi nd a perfectly acceptable version at your local electronics store. For both indicator-signal bulbs, you’ll need a 6-ohm, 50-watt resistor, connected in parallel with the filament; that is, one end to the 12-volt supply wire and one to ground. Be aware that the resistors can get hot, so don’t mount them in contact with anything plastic. Installing LEDs in the front too? That means doubling the number of resistors.

There’s more: some vehicles with burned-out-bulb notification on the dash will similarly freak out when incandescentlight marker bulbs are replaced with LEDs. Treat them to the same add-on resistor cure. Since the marker lamps draw less current than the turn signals, use a resistor that draws less current: to wit, 25 ohms and 25 watts. This puppy will also get plenty hot, so be careful where you mount it.