Armstrong cutting out during daylight hours

I have the original Armstrong on my 77 excella 500. It is parked in the sun. During the heat of the day, the compressor will run for about 30-60 seconds and then make a "loaded" sound and then cut out. Once the sun goes down, it functions just right and cools the trailer perfectly. Unfortunately, the trailer is 60 miles away. After reading other posts, I am not certain if it is the run capacitor or not. Heck, it sounds like it could also be the external fan. I will probably just buy some parts in speculation of the fix prior to my next trip this week. Any suggestions? My voltage in the trailer is 111v even while the compressor is running.



Thomas