Motor run capacitor now has half the expected capacitance

[e100]

Had a power cut that affected several houses including mine and it took several hours to be fixed. The repair guys were working in or around the local street transformer but I don't  know what went wrong or what repairs were made.

Once the power came back on everything in the house started working,  except for a single phase induction motor that now just makes humming noises.
I pulled the capacitor out and it measures 8uF instead of the 16uF on the label.
Is this a typical failure mode for motor caps that have been stressed beyond their rated voltage?

Mike

[dfmischler]

Caps fail.  Cheap caps fail quicker than good ones.  Attributing this failure to any particular event is probably impossible.

I have some Reznor UDAP-225 heaters at work that run on 230V (a nonstandard option in the USA).  All of the factory motor run caps failed in the first two years.  I keep multiples of that cap in stock now because there doesn't seem to be any other choice.

[wraper]

It's self healing capacitor. Once the short appears, part of the materialization burns and capacitor still works but with decreased capacitance. Such fault is not uncommon. Motor caps are usually even marked for how many hours they are rated.

[kleblanc]

Run Caps go very often especially when the equipment is always on. I service HEPA airflow equipment and always have 1 cap (5,7.5,12,15, and a 25 to start locked fans after a decontamination) uF with me.  You only notice the problem after power failures or when the equipment gets turned off and the users try to turn them back on.