I have mentioned this before, I am in the controls / instrumentation industry. I recently found this kijij ad:
RV mechanics diagnostics tool PAL Dometic fridge tester
NOS from the mid 1990s PAL fridge diagnostics tool for Dometic fridges. Worth hundreds asking $50 obo
Now, I don't think a diagnostic tool from the 90's is worth $100's, but since PAL is a current fieldbus protocol for vehicles, (OBD II) it may be possible to use other tools, but with a cable adapter.
Being the geek that I am, I'm considering purchasing this relic, even though I donít own any of the fridges that it works with.