How did you determine it was the oil sending units? I had an low oil pressure warning light go off on one of my engines but it was just fouled up spark plugs. Once I replaced the plugs with new ones, that fixed my problem and cleared the low oil pressure warning light.
Not sure if there is more to it that makes you think it's a wire or sensor, but i'd check your plugs first, if you haven't already. If you have, then someone else may need to chime in as I wouldn't be sure.