Ever so often my cars lights pulsate. This only happens when the car has sat in wet weather or is driven in slushly snow. The pulsating only lasts 1 minute or so then disappear. I've misted the engine with water trying to replicate the symptom with no luck including ground points. The belts are good and tight. The belly pan is on. Not sure it's the voltage regulator as it only happens in certain conditions. . Any suggestions would be great.