A/C unit cycles on and off during cooling phase

I ended up pulling the capacitor and testing it with my ohm meter. It was dead. I could have easily gone to the local HVAC supply, purchased a new capacitor for $30 and installed it myself. But, because I also wanted to have the pressure tested, I called in the guy who installed my furnace. He affirmed that I "did good", it was the capacitor. And because I had done most of the diagnostic work, he cut me a good deal.

In the end, the most important bit, on a 95 degree day when the humidity is 70%, a happy wife is a blissful life. ;)

There is no problem with the unit running continuously without a break. The most wear occurs when the compressor starts up from being off. A unit that is sized to run continuously is actually more efficient than one that cycles on and off.

We have a slightly undersized Carrier central a/c unit (12 SEER) which is 26 years old, but still works as well as could be expected for one that age. The blower fan motor is original and the compressor is original. The original fan in the condensing unit failed and was replaced 2 years ago. On very hot summer days (>100 F) it turns on at say 11:00 am and runs continuously until 5 pm.