can a 1.68A fan be used with a 500mA power supply? (at less fan output)
I plugged it all in - by the way, the power supply is only 500mA at 12V. The fan was pushing so much air! 
this is the datasheet, it's a beast of a fan - i pulled it out of a server. 
https://www.digikey.com/htmldatasheets/production/2084948/0/0/1/pfc0612de-f00-spec.html
rated for 1.4-1.6A. 
seems to have been working all right, may be to the same capacity as it was before. 
only thing was the power supply was warm to the touch after it was on for 5 minutes.i mean warm to the touch