No, they didn't come with faulty wiring, its that with age, the wires and the contacts get a thin layer of corrosion on them. The contact point at a connection is decreased and the amperage going through the smaller connection builds resistance which turns into heat.
Pull the plug on the light switch and view both side of the larger red wire going into it. Check the black plastic around that wire to see if its melted or burnt. If not, pull the switch and inspect the dimmer ring and contacts. If nothing else, take some sandpaper and scuff the contacts of the switch and use some grease to protect them from moisture.
Oh, and carry a fire extinguisher if you don't have one.
1975 CJ-6 304 T15 Dana20 30/44 3.73
1983 CJ-8 258 T5 300 30/44 3.31 Looking for full or half hardtop buy or trade
1986 CJ-7 Laredo 4.6 stroker T5 300 30/44 3.31
1986 TJ-7 Trail Jeep project in the works
2003 Inca Gold TJ Rubicon