Put in a new Battery, got nothin' - I am not dumb, but maybe I'm not bright?

[SPYDERLK]

I use my test light to put a small load on small gauge wires but that wouldn’t prove anything on starter cables.

It would assuming normal discrimination on the ~ 20 V range. Normally the lowest applicable scale for 12V will discriminate to the second decimal ... (0.01V) .

For example, as in the OP case say the battery terminals are 12.63 NO LOAD. With a meter set up to apply a 1A load thru its leads the measured voltage may be 12.59. The loss is from slight battery suppression and loss in the meter leads carrying the current. Now move the Neg probe to a clean chassis ground .. 12.58 -- probably ok.

Affix that probe securely. Now move the + probe from + terminal to the + clamp .. 12.55 -- something wrong there - fix it. Now move the probe onward to the lug at far end of + cable .. 12.56 -- probably ok. Now move the probe to the stud the lug bolts to .. 12.47 - FIX IT. (That loss of 0.09V at 1A would equate to a loss of 9.0V at a 100A starter draw - no response at all, or a chatter click.)

Now, the starter should operate. Remove the meter load setup and get some help while you assess each of the previous connections under the substantial starter drain.

 

[Fuddyduddy1952]

If you ever have an open electrical wire you want to splice simply pull on it...insulation snaps where the break is.