I've got a '98 Durango 4WD SLT+. I dont know why, but it just started happening today. I turn on my right signal and its all fine. I turn on my left signal and it seems fine... until i hit the brakes, then it goes into hyper flash. It has all LED signals front and rear, with a resistor on each circuit to make up for the lack of resistance in each bulb. I've never had this happen before and now in one day, it goes from acting normal to having these symptoms every time i put use the left signal

 

i would start by checking for a short, quite possibly on one of the brake lights.

your going to need a multimeter with continuity and some patience, also the wire diagram found in the FAQ thread would be helpfull as well.

 

okay. ill look at it monday. im busy until then. I have the huge factory service manual with all of the wiring diagrams so maybe thatll help me. also i just remembered this, I have LED bulbs in place of all three of the third brake light bulbs places.. maybe ill first try to replace those with the factory incandescent's before anything else. Maybe not enough resistance in the third brake light circuit because of the LED's and it's finding ground that way? I dont know but its worth a shot i guess