.................. you need to do a voltage drop test on any questionable section of wire.......................You can see why this is bad, and you can see how it would fool a simple resistance test.
That's a good plan but you left out one important piece and that is CURRENT. You cannot measure voltage drop without current flow.
One easy "backyard way" is to simply put as much system load on as you can, IE, with the engine off, turn the key to run, turn on heater blower, lights, etc, and then measure voltage, first at the "input," which is essentially the starter relay battery stud, and the "output" which is where the fuse link ends at the bulkhead terminal it feeds.
This is why, tho, that I asked for more details. Without knowing what the OP is fighting in the way of trouble, hard to advise.
