air compressor won’t kick on by itself

A friend is near Memphis is having compressor trouble. If he takes off one line at the governor and lets the air bleed off that line, puts the line back on the governor usually the compressor will pump ip then. I don’t know which line he was told to remove, bleed and put back on. Any ideas? Tia

 

Thanks. It turns out his boss is too cheap to do the job right. Previous compressor went bad. He had a shade tree alcoholic put on a replacement. The system wasn’t cleaned of all the oil. A new filter wasn’t even put on. The cold was was causing the air dryer to not work properly. He is going now.