3 wire LP detectors that had a 12 volt solenoid were common years ago. But, OEM's and Rver's got tired of false trips that caused loss of LP when the LP solenoid shut down. There is NO code that requires an LP detector shut off system. So, when the original LP detector failed you installed a standard LP detector and REMOVED the 12 volt solenoid at the tank regulator.
There are 2 types of 3 wire LP detectors.
1. The one with the cut off solenoid as above
2. The other uses a positive wire from the coach AND a positive wire from the chassis to make sure the unit always had power. Doug
