I just changed to led tail/brake lights on my 08 f-350 superduty and now the turn signals blink fast but the emergency flashers are normal. What's the deal? TK

 

Some flashers work off of the current that the bulbs pull. When the current drops, such as a bulb burning out, they flash faster. LED's use very little power, so they flash fast. You can solve this by putting a resistor in parallel with the LED or getting an electronic flasher that doesn't depend on current to run. It doesn't do it with the emergency flashers because you still have regular bulbs up front.

 

You can use a different flasher to resolve the fast blinking, but you need resistors on the brake circuit. The brake circuit is biased, and unless it has sufficient electrical load, other systems make not see the state change in the brake circuit. A couple years ago I had my transmission rebuilt. I had it overbuilt to make sure that it would be able to handle what I do (I haul a lot of loads and occasionally pull a trailer), frequently up to a ton. Now this is nothing for a Super Duty of course, but for an Aerostar, that is a notable amount of weight. The shop upgraded a lot of parts and I spend a good amount on the trans. I installed LED brake and tail lights. Because of the way the brake circuit works, the computer could not tell the difference between when the brakes were applied and not. The computer could detect the circuit bias, and read that as though the brakes were on all the time. As a result, the torque converter clutch did not engage, resulting in excessive heat, which in turn caused my overbuilt trans, which should have lasted at least 150,000 miles under the kind of use I did, to make it about 40,000 miles, about 30,000 on the LED lights.

The point of my story is, play it safe, install the load resistors on your brake circuit, its not expensive, it won't hurt anything (if installed correctly), and will act as insurance that the computer and other systems will see the brake circuit correctly. As for the blinkers, a HD flasher will take care of that issue. You could also do load resistors too.

The main benefits of LEDS is not their low current draw, its the lifespan, the brightness, and the instant on. So you will still get all the benefits you originally installed them for, but with resistors, they will still need as much juice as an incandescent.

 

I'm not positive, but on an 08 I believe that:

A: the flasher is built into a module and not serviceable

B: I think that I remember reading that the computer can be reprogrammed for led lights to work correctly.