The ORIGINAL system had an LP detector inside that has a switch on it. The Detector HAD to be ON for that solenoid to open. MOST of the time, the inside detector is too OLD or is bad. There is no code or requirement you have to have a LP detector/solenoid system Most people remove that solenoid. The only exception is if you cannot get to the LP tank manual On/Off Valve without crawling underneath the motorhome. In those cases you must have a electric remote shut off switch for the solenoid. BUT, THAT solenoid is between the Tank valve and the LP regulator. IF your solenoid is after the regulator, just remove it. Doug