A few melted spots in headlight harness

Driving my 68 Valiant the other night, the headlights crapped out, but the brights still worked. Went under the dash the next day to investigate and noticed that all 3 wires going to the dimmer switch were melted together. I had previously replaced the switch, so all the connections were ones that I had made. Remade all the connections, everything worked again, but whenever I have the headlights on, I can smell the beginnings of those wires melting back together. Today I went to chase the problem down and pulled the headlights, passenger side was good, but driver's side had the red lead's housing looking kinda melty, not super bad, but enough to make it harder to remove. So if I'm not mistaken, this points to the driver headlight being the problem? Running cheapo aftermarket halogens, just bolted them in place when I was 16, never thought twice about it. I'm thinking about buying new headlights soon, do yall think the halogens are what caused the problem, or just old car with shoddy wiring?