Our manifold is ugly, but it works. We’ll do something sexier later. Note the compact, 12-volt pressure switch (A) that’s smaller and cheaper than 110-volt pressure switches—and it will better withstand mud and water. The check valve (B) is required to prevent the system from leaking back through the compressor when it’s not running. You should also have a safety valve (C) to prevent the system from becoming a bomb if the pressure switch fails (these compressors can go to 400 psi), and a dash-mounted toggle switch. A gauge (D) is nice but not essential.