I would check the fuse first. The fuses are behind the RH side panel. Did anything else go out? Is this an 800? 600? Is it an X model? If the fuse is good (and firmly in place) you can trace the grip heater wires from the grip to the plug at the handlebar riser. Unplug them and test across the grip end plug pins for resistance using a VOM. The very early 2008's had some issues with the grip heaters going out but I haven't heard about any known issues with the later models.