Three or 4 things will cause current demands to increase on an air conditioners.
LOW VOLTAGE has already been covered so I'll leave that here. I will let others discuss things that you may be able to do (like cleaning the plug) to help out here.
AGE: not likely the culprit but as the motors grow old bearings and such can wear out and increase drag. I do not believe this is your problem
The last two are very much related.
HEAT: As the mercury rises, so does the head pressure the compressor is working against and thus its current needs.
DIRT: epically on the condenser coils.. As they clog with dirt and stuff (Tree Dandruff) air can no longer flow across the fins as well, this results in the coils not coolin off as well and .. Well See HEAT above.
FACT: one of my 13.5 amp units started tripping its 20 amp branch breaker.. I metered it,, started out at 13.5.. climbed to over 21 just before CLICK.
I cleaned it
13.5 and holding.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times