A few years ago an elderly but still cyclist neighbour told me about that hack. To reuse a fridge motor as an air compresor, mounting It on a wheeled table (because It weights enough to need them) and wiring It to be able to turn It on and of while conected to the grid (with power interruptors, of course!)

I only needed the motor (with their 4 big screws and nuts), the table, 4 wheels, a few decimeters of plastic tube (depends on motor output diameter) and in my case I attached the balloons valve directly with a metal clip.
For the air input you could use any kind of filter, to avoid jums.

As far as I am aware that motors do refrigeration by the fluid on It, so working with It empty (with air) would raise their working temperature quickly, so it's easy to burn it!

It is full of dust now, but It was a honor to inflate balls using It.