Exactly the opposite Dan. LED's draw so much less current that old style flashers (signals and 4-way) wouldn't work with them. Typically, an LED taillight will draw about 1/10 the amperage that a regular incandescent bulb would. With old style "standard" flashers that meant that not enough current flowed through the flasher to heat the bi-metallic strip (which bent to open and close the contacts) so they never flashed, or flashed very rapidly (because the strip cooled quickly). However, if you install what is normally called a "heavy duty" flasher they will work just fine. Heavy duty flashers don't depend on the current going through them to the bulbs in order to flash. Instead, they have a built in resistor that provides the "load" needed. They were originally made for use on vehicles towing trailers, because the lights on the trailers added to the current draw and overheated a standard flasher. The standard one would flash once, then stay open, or just barely let the bulbs flicker. As a matter of fact, I had that exact same problem on my GMC when I first bought it. The turn signals would suddenly stop working after the truck warmed up and they got used a couple of times. Turned out the normal heavy duty flasher had been replaced with a cheap standard one, and the heat from the engine (June in Florida, with a diesel) was just enough through the firewall that the flasher got too hot. Now, they do sell special "electronic" flashers for use with LED's. The only difference between them and a heavy duty is that the electronics also have additional circuits in them because some vehicles have odd flasher circuits, and adding LED's to them can lead to problems, like brake lights not working. I believe this is a problem only on vehicles with those oddball turn signals where there are separate lamps on the front and the sides that alternate when they flash. Not 100% sure on that though.