meter checks
yes unfortunately, broken or partially broken wires can often ohms check good for continuity and you can read power across them too sometimes
The problem is while you may need to carry some current all you got is the potential --- all it takes is one or two broken strands touching and you can read continuity and voltage--just don't try to run anything from them
You can prove a wire bad by Ohms check but you cant prove it good
What is actually better that is likely to be in your garage at home is is a load lamp, or a couple bulbs wired together depending on what you are checking ---that puts a little load on the wires
If they are broken---That's just a limitation of the meter, normally works fine but that is one gotcha with a multi-meter
just something to keep in mind
I went back and looked at the pics---dont look that bad? How did your mechanic determine the wires were broken? I hope that that is not a guess cause he cant find anything else