Pulsating Headlights

I would start with the voltage regulator. Adding Crackedback's headlight relay kits are a good idea as well. I have a theory what is happening but I don't want to embarrass myself, oh hell here goes, high resistance in your light circuit (headlight switch or other) is causing the voltage regulator to toggle, once the load increases the VR closes and goes straight on alternator power. Just a thought-------------------