The hand warmers on this sled would get warm but not hot, the thumb warmer was cold,I checked voltage with nothing plugged in and it was about 15, when I plugged in the hand warmers it would drop to 11 volts, then when I plug in the thumb warmer it would drop to 10 volts at 3000 rpms, the fix was- anyone ever wonder why there are two voltage regulators? yes the one with four wires is for the grip warmers and it was bad, replaced it and now the thumb warmer gets hot, problem solved.