why low pressure gauge on R-11 chiller would
go from 14"Hg to O and back to 14" in about 10 seconds?
After seeing it twice I decided to find out what was going on.
It didn't take to long to get the answer.
I will give you only one clue:
Nothing noticeable different was happening in operation of the chiller during this event. No change in sound of the motor and no change in amp draw.