 Gabe Hart had him do several things from turning radiator fans on and off, giving him the different readings, to cycling his alternator light as well. Right now, Hamlin, under low RPM, has a red light flashing in his car, signaling low voltage. The other thing Hamlin's having to do is cycle on and off his cool suit. Gabe Hart told him he could turn it back on for now, but if the light comes back on, he's going to have to run without the cool suit.