When you turn the headlights on, I get a low pitched squeal through the speakers,and when I accelerate the frequency of the sound gets higher in pitch, and does not stop. If the headlights are left on and I turn the dashlights off, the sound is not there.

Since it happens with the lights and the accelerator,It is the body ground module that is either loose or damaged.

Hi and welcome to FixYa,

Your described concern almost always indicates an alternator issue. More specifically, the regulator. The actual term is "alternator whine" and since it is coupled to the engine by the belt, the pitch would be affected by the RPM. The whine also rides on the DC voltage since the alternator charges the battery and therefore could be heard on the speakers.

A temporary workaround is to install filters/condensers to shunt the whine to ground although in the long run attending to the alternator now may be to your best advantage.

Good luck and thank you for using FixYa.

You have either a bad ground or a bad switch for the dash dimmer since the noise goes away when you fiddle with the switch. thx peyton

Welcome to Fixya! You have a Bad Ground Either inside the Dash or the Battery Ground is Loose. It could also be the Switch for the Lights that is Grounded. A Bad Ground will cause the Squelling through the Speakers. Please Rate My Response! Thanks!