Hey! We thought maybe you could help us! We bought a 1998 American Eagle on a Spartan chassis. There is an air valve on the firewall with two solenoids that supply air to the blue hoses which supply the front and rear air bags. We pulled the supply line and no air. We traced it back to the tank where it looks to be a pressure regulator. We took off the hose and no air was coming out of the regulator. We replaced it with a new regulator of the same brand and still no air coming out of the regulator. Spartan has it labeled on the schematics, that we got from Spartan as a safety valve - we don't know if that is the same thing. Is an air safety valve and a pressure regulator the same thing? Is a safety valve a one way valve so air can't bleed back into the tank? We think someone prior to us replaced it with this pressure valve and maybe it's the wrong part? We are going to call Spartan tomorrow but we saw you had helped others so we thought we'd see if you could help.