Double DC Motor Compressor Circuit Protection
Have you considered using solid state components like MosFet transistor in an half or full H-Birdge sturcture  pattern ? 
According to me, it's not really usual to use relays for driving motors but maybe I am wrong. I hope more experienced contributor will explain why. But reliability and high voltage spikes may damage your relay fastly.
Below a starting point.
https://en.wikipedia.org/wiki/H_bridge

Sorry by advance if my answer doesn't help you much.