they can be checked one at the time but it is tricky: Using insulated tools and gloves you would remove one wire at a time put it back then another then put it back and so on till said switch is found and you would then replace it. Harper Wyman is a leading manufacturer of these type switches by the way. Mostly the recommended thang to do is replace the whole damn harness but who has the money these days?
Seems that my right hand is hurting somethang fierce and I cant type worth a dayum. I need a beer.
maybe some dang whiskey yeah dats da ticket