I know some fan motors have ports to oil but many do not (bathroom exhaust fan, bathroom heater fan, regular house fan, etc). How do you oil the ones that do not have ports?
Specifically, where do you put the oil 3-in-1 oil?
Edit: The model I'm maintaining is NuTone 765HL (https://www.broan-nutone.com/en-us/product/ventilationfans/765hl) ad it says the heater fan is sealed but doesn't mention anything about the vent fan.