My front Coleman unit was short cycling and at first I thought the compressor was just tired. It would start then click off and try and restart and pop circuit breaker. I shutoff the power and went up on the roof and opened up the electric panel and discharged the capacitors. I tested each capacitor and found my start capacitor out of spec, There are 3 capacitors one for the fan one for the motor start and one for the motor run and also a potential relay. I took a trip down to ww,grainger and got new ones. anyway the compressor still was short cycling,so I did some reading about the potential relay and how to test it. The relay is normally closed between term 1 and 2 . I took my ohm meter and verified it had continuity,it did. the schematic showed that I should see some resistance between term 5 and term 2 mine didnt. I went back down to town and bought a new relay,problem solved.
.Here is an explanation on how to test it
Troubleshooting The Potential Starting Relay (http://www.achrnews.com/articles/90387-troubleshooting-the-potential-starting-relay)
Here is the relay I replaced mine with
UMSR-50 - ICM Controls UMSR-50 - UMSR-50 Universal Motor Starting Relay (http://www.supplyhouse.com/ICM-Controls-UMSR-50-UMSR-50-Universal-Motor-Starting-Relay?gclid=Cj0KEQjwid63BRCswIGqyOubtrUBEiQAvTol0ZUfHVt0WTwGH-y3QOGvAUzB6jgF1opywPXSb5V3eLkaAmy08P8HAQ)
Glad you found the problem, and good technical write-up! I love reading about true troubleshooting!