Thanks for tips. Update:

Pulled my heater motor and it wasn't too bad of a job. Found out that the motor was almost seized. I lubed it and it seemed to spin well after that. i wasn't able to find out how to get to the regulator.... It put the motor back in and everything seemed to work pretty well. Hi, low and auto works - maybe hi speed wasn't really fast enough? Not sure about it.

However a few weeks later after filling gas and starting the engine again the fan was dead again.

After that it suddenly started working again a few days later - everything seemed normal. Has been like this for the past couple of weeks. Works normal for a while, suddenly stops working, but starts working normal again a few days later. Very bizarre.

Must be electrically related. Some sort of relais? Or simply the regulator - can it behave like that? Any tips would be appreciated!