[mrein3]

MN location. (Like me).
Most likely a green, furry dimmer switch connector.

Step 1: Take the connector off the dimmer switch. Look at the connections.
Step 2: Spray with contact cleaner.
Step 3: Re-connect.
You probably just fixed your headlights but I'd do more...

Step 4: As 72SB points out, research this site for "Headlight Relay Upgrade" then roll your own or buy a pre-made wiring harness that uses relays to power your headlights instead of elevendy billion miles of 16 or 18 gauge GM stock wire.

All those miles of stock, too small now dry and brittle wire only gets about 10.5 volts to your headlights.

Using relays to drive your headlights with juice straight off the battery not only puts 14.something volts to your headlights making them brighter, it also saves on your headlight switch which is more money and a larger PITA to replace.