You are right piperjon you do need a resistor that will consume 21 watts of power (on all four corners if replacing all Flashers to LED's) you can in effect use the original 21 watt bulb mounted in the hump or somewhere.
That is why I am recommending paying the extra to buy an electronic Flasher unit to drop down the power usage of the indicators, why mount a resistor that acts like a mini Bar heater converting electrical energy to heat when you are mounting LED's that have the main benifit of using minimal power.
It is just a drop in unit, no modifications at all
It will even work with normal 21watt globes Back and Front or using=42Watts
Globes Front, LED's Rear or of course using=21Watts
LED"s Front and Rear. =negligible Watts
That is why I am recommending paying the extra to buy an electronic Flasher unit to drop down the power usage of the indicators, why mount a resistor that acts like a mini Bar heater converting electrical energy to heat when you are mounting LED's that have the main benifit of using minimal power.
It is just a drop in unit, no modifications at all
It will even work with normal 21watt globes Back and Front or using=42Watts
Globes Front, LED's Rear or of course using=21Watts
LED"s Front and Rear. =negligible Watts