Why do my headlights go off but my clusters lights get brighter as I step on the gas pedal?

Why do my headlights go off in my 1990 honda civic and my clusters lights get brighter and my heater blows air harder as I step on the gas pedal? Can some one please help me

But if it was my alternater wouldn't my sterio go off too like my head lights?

Weak battery or altenator

Yeah either a weak battery or alternator. You can have them both check completely free at somewhere like auto zone out advance auto parts. When this happened to me it was my alternator going bad.