Change tracking is always very tricky. Depending on the specific requirement, usually I also try to evaluate other options:
- is it possible to track changes as they occur? (e.g. a few lines in a user exit writing into a custom table might be easier than a "search expedition" afterwards);
- is it really necessary to track the changes? (e.g. if it's an interface to an external system, it's sometimes easier to just dump all we have in SAP there and let the other system sort it out).
Unfortunately, I'm not that familiar with equipment master to confirm table links, but it's clear that first approach doesn't cover all the bases, so it would have to be combined with the second approach. I didn't quite get why you said it's working till step 5. If you have EQUNR, why can't you get the data?