The round usually black in color "klixon" is the overtemp/circutbreaker. & if the start-run relay is also the "klixon" brand, then it is obsolete & isn't available anymore, but you can replace it with a new 3-in-1 solid-state start-run relay with a built-in overtemp protector, it is very small & comes with 4-5" wire leads to attach to the compressor connection pins.
here is a link to Graingers online catalog with the Item page.
http://www.grainger.com/Grainger/items/4E238http://www.grainger.com/Grainger/items/4E238
