Here's a post from this website that I cut and pasted. It was EXTREMELY helpful when I installed Dual Stars on my 05. Good luck.
Yes, I just put the DualStars on my '03 Sprint last week. They work great! I have no comparison to the Factory ones, as these are the first heated grips I have ever had. I got the three position round plastic switch and left bar insulator that dual star sells. The install under the factory grips was easy. Use a butter knife w/ some dish detergent on it, grips should come off no problem. When re-installing them over the heated elements, I used some hairspray on the inside of the grip, and on the bar, slips on easy, dries tight.
Make sure you buy a 12 v. automotive relay. Tap into the special wiring in the left side of the fairing for the factory heated grips. MAKE SURE YOU DO IT with the relay. I tried both wiring it directly to the unswitched wire, which works great, but if you EVER leave it switched on, it will flatten your battery, or using the switched 12v wire, problem with that is it doesn't get anywhere near as hot, and takes longer. Use the relay and have the best of both worlds.
I also drilled a small hole in the left fairing below the left grip to mount the switch, looks factory. Be careful when you do this!
FYI- on the special wiring harness, the black wire is the ground, purple is unswitched 12v, and grren/ grey is switched 12V.
I got this advice from CLB on this board about the relay:
The grip heat connector on my '06 is located under the headlight on the left hand side of the fairing.
The connector has 3 wires. Those wires are ground, constant 12Vdc and switched 12Vdc.
If you have a meter you should be able to figure out which is which.
If you don't have a meter... Buy a meter.
Automotive relays generally have their terminals labeled 30, 85, 86, 87 and SPDT relays have an additional 87A contact.
It doesn't matter if you buy an SPST (4 terminal) or SPDT (5 terminal) relay. If you buy an SPDT (5 terminal) relay you will leave terminal 87A unused.
Buy a relay without a coil diode so you cannot wire it backward.
Wire ground from grip accessory connector to terminal 85.
Wire switched 12V from grip accessory connector to terminal 86.
Wire unswitched or constant 12V from grip accessory connector to terminal 30.
Wire terminal 87 (normally open) to your heated grip power switch and on to the heater elements.
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