Re: vacuum fans
I've played with a few. The main problem with them is getting lube to the shaft. They gum up after time and also accumulate 'lint' blockage under the cover around and behind the rotor.
Trying to pry off the rear cover is difficult. I have had success holding a finger over the hose barb and blowing full pressure shop air into the intake hole with a rubber nozzled blowgun. The covers pop loose and you can then remove them without making ugly pry marks on the pot metal.
Once open blast it with brake or carb cleaner then squirt light oil behind the rotor onto the shaft. Park it rotor up, fan down for a few days to allow the oil to flush out the shaft. Rotate it back/forth every now and then.
When it spins free clean everything up. You'll need to apply a tiny bit of sealer on the rear cover, it needs to be vacuum tight. The last one I opened had nothing but the paint as the seal.
To test them (and give them a good high speed workout to loosen them up) I used my refrigeration vac pump. If you hook it up through your refrigerant gauge set you can bleed air in and watch the gauge to see it work at 5", 10", 15", 20" vac.
Good luck. Being die cast zinc (potmetal) I'm sure some of them have suffered the same fate as vac wiper motors and Tilly carbs.
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