Headlights are dim or don't come on

[custom10nut]

I hope somebody can help me. I bought a set of halogen headlights for my 70, but when I pulled the switch, they wouldn't come on. Checked the connections, and played with the dimmer switch, and I got them to come on, but only on low beam, and they're very dim. I thinking either it's the switch, or the connections under the dash. The markers are doing goofy things too, so I think it may be the humidity that corroded the connections.