Strange noise from heater box when headlights are on
 

How are all you gearheads doing. I ve got a strange problem with my 72 Charger SE. When the (hidden) headlights are on, after a few seconds a noise inside or near the heater box starts screeching and/or clicking. Looked in the service manual and parts manual and found nothing but vacuum controlled valves on the outside of the heater box. Anyone have any idea what the problem is or heard of this. Why this happens only with the headlights on is the mystery. Question is what does the headlights have to do with a vacuum system? Thanks. dgbcharger :yikes: FYI.... Found IT! It was a bad headlight door motor relay under the dash above the heater box.