Central Air Conditioner (house trailer)

Question

I have a central a/c in my trailor. All summer long it would only come on when it wanted to. It may come on but after it shuts off it may not come back on for a week or two. I tried changing the thermostat but it kept doing the same thing. Could the problem be some type of relay switch in the a/c unit itself? I appreciate any help or suggestions someone can give me.
(I don't know the a/c brand name / its works by itself and not off of a heater thermostat)
Thanks so much :)