As rescue dog stated (and read his attachment all the way through) there are many reasons and possible issues. We have found that the draw from led lighting is very inconsistent hence the use of a load resistor which will help stabalize the draw much like what is always needed when using led turn signals. This fix has worked for us many times which is why I recommended it as it is a very low priced possible remedy.
The reason for using load resistors with LED turn signals is simply because the old style bi-metal flasher doesn't get enough current through it to heat up and open the circuit. That's how your turn signals flash off and on. It heats up and the contact points inside open and the lights go off, it cools down again and the contacts close making them go on again. If you have read much about it, instead of using load resistors, you can simply use an electronic flasher to replace the mechanical one. It blinks at the same rate no matter what the load is on it. Using the correct flasher is the way to go. Adding load resistors is a hack in my book. Especially when some people want to use an LED because they take less power, then they add a load resistor and are back to drawing almost as much as the incandescent lamp.
This goes for most cars and trucks on the road. Newer ones with a CAN BUS where the computer see's a small load thinks (if a computer can think?) it thinks that the bulb is burnt out and it tells you with a dash indicator light.
The article in that link has a few flaws to say the least, but I'm not going to get into that here and now.
www.octanelighting.com
