You will often start to hear extra fan noise if the bearings are going. I bench test them and note if it seems to struggle to spool up, especially just as it receives power (there's a huge draw at this point).
You could use an inductive ammeter I suppose - it's not something I've done.
I installed a 60 amp relay and until now it seems to have alieved the situation. I also put a 40 amp relay on my fuel pump wiring. thanks for all the help!