The original Grote LEDs did not have a load resister built into the light, and what happened was the flasher unit could not read the signal that was being produced by the turn signal control when activated. There simply was not enough amps drawn by the LEDs to cause the flasher unit to react.
It was found when used with the flasher control that AM General, was installing into the HMMWVs.
Grote came out with a HMMWV retro-fit kit that addressed this after it was discovered.
When I was restoring my duece, I met with a Grote Rep, at the Mid America Truck Show in Louiville, KY.
He explained this to me, and told me that the kit came with a B/out Headlight, two front turn/marker lights and two taillights. He also said that any one of the lights by themselves had enough resistance to operate the simulated load needed to "trick" the flasher unit.
You will need to contact Grote, in order to get the resistance module that goes inside the light housing. This will correct the condition.