Once the first switch heats up and burns, you may find that the matching plug on the harness has been burned also. Plugging a burned harness plug onto a new switch will again cause a loose connection that generates heat. And the cycle repeats, headlights blink and another switch burns up. Check the plug. Another problem with these (as happened on my '90 Dakota) was the headlight lead wire burned at the bulkhead connector where the circuit passes through the firewall (Driver side near where the steering column passes through). Pull the cover and you'll find a green corroded connector. I pulled wire straight through the bulkhead and spliced the wires direct without connectors and sealed it back up with silicone, permanent fix.