I feel like it would probably be inconveniant for him to just randomly cut them until he gets lucky....

 

theres only 3 wires. cut them all, disconnect one at a time. you only have ~3 options. resolder. ten minute job. if you really want we can dig up a diagram.

 

If you have a voltmeter or test light, just have someone turn on the parking lights and see which wire gives 12vdc to ground. I believe you can tell from inside the socket which wire is which. That'll be the one you want to cut and seal off