First the UOC. Did you notice in the -24P manual, that the thermal watt converter, (TWC from now on) is listed twice? Look at the manual. Item 31 I think is the TWC. Listed twice, different part number and NSN. So what's the right part for your set? In the first few pages of the TM, there is an explanation of terms and a "how to use this manual". Towards the end is the explanation of the UOC. In it, it lists all the model numbers for the different gen sets. And there are several. You have a MEP-004A. Look to the right and you see CLD. That is the UOC. Now look at the two listed TWC's, and notice that to the right of the NSN's, are the UOC. Pick the NSN with tour UOC. Some people assume, and that will get you in trouble every time, but they assume that the 60 hertz (MEP-004A) parts are always listed first. It ain't so. Learn what your UOC is, and always look for it. 99.99 % of the parts fit all models. But it's that .01 that will mess you up.
Now, to the testing of the TWC. If you looked at the procedure. Can't do it with your multimeter. And you can't do the test for the M4, (watt meter itself) because you can't close the output circuit breaker. So we need to get that to close first. You said in your first post that if you use the battle short, you can get the overload relay to function right, but " the set has no power to start". By that you mean the gen set will not turn over and start? That's normal. Try first starting the set, flip the battle short up, and then push the output circuit breaker to the closed position.