Switch needed

That is the key in warning buzzer switch. I found a new one on eBay for mine. The question is what caused it to melt down? The buzzer is in the horn relay and is supplied 12 volts looking for a ground thru the switch to the driver door switch on my 71 Demon. I also replaced the molex connector on the ignition switch with a weather pack connector due to the new wiring harness in the car and the new ignition switch making poor connection with the new parts.