When I added the 3157 LED Bulb - Dual Function 28 SMD LED Tower - Wedge Retrofit bulbs (which are awesome) to my 1999 Ford F-350, I had to use the in-line resistors to stop the hyper flash because this flasher wasn't available. My recommendation is do not splice anything in-line. I had problems of shorting and the resistors getting hot. I replaced my standard flasher with this LED flasher. I removed the resistors and all is working good. I recommend using the flasher instead of resistors.
I bought a used Ford Ranger where the LED taillight bulbs would not complete the circuit on a factory or heavy duty NAPA flasher relay. Must get the LED specific relay this one worked great, arrived fast and was cheap.
Perfect fit - a bit difficult to install (had to take entire lower dash panel under steering column off to access the old flasher.
Works great and solved the hyper-flashing problem I was having with installation of my front and rear turn signals/brake lights.
Took 10 minutes to change in my 1999 Ford Expedition. I have LED front turn signals and LED tail lights. Did not get the hyper flash until installing the front turn signals. Changing the flasher fixed the problem. I used a plastic trim remover to remove the old flasher. Took me 5 minutes to figure out that the plastic cover over the flasher was taped closed with electrical tape on the side that i could not see.
Lost the right hand turn signal in my 2001 F-350. I replaced the multi-position switch and that didn't fix things(but did fix other issues), so I ordered this. Simple plug and play and my turn signals work again. Has a perfect flash rate, loud click to let you know it's working, and drives all of my LED bulbs without the need for resistors. Nice price to boot!