I was cruising around at night and all of a sudden my lights dimmed, I watched my volts drop way below normal, and the engine almost died. It was instantaneous and recovered immediatly. The SES light flashed real quick, however I retrieved the codes and none were set. It happened again later in the night (this time it wasn't as bad and seemed to happen at the same time I shut my heater off). No SES flash the second time. Any ideas what could cause this? Are these signs of an alternator going? Or could it have been my radiator fan kicking on?