Independant elements can go bad, as they are 2 individual heating coils. If the ground breaks, than they will both fail. If you can isolate the wires to that grip, use an OHM meter set to 20vAC and see if you have voltage between the ground and both pos. wires, one for high, one for low. In either case, if they don't work you will have to replace them.
Another option, one that I use is to put on the sissy mitts(gauntlet style covers), I like to wear MX style gloves, and I stay warm on the low setting.
Jim