Power: LP Gas Sensor

The LP Gas sensor is getting some power, but in the millivolt range of my multimeter. It's definately more than when I touch the probes together.  But why? Shouldn't it be at 12V? Anyways, this is a DC system and for all I know it's connected to the auxiliary generator, cab motor and converter not charging the auxiliary batteries, which apparently run the display panel with all the level indicators for things like the boondocking water and liquid propane gas tanks.

New Faucet Installed: Bathtub

I installed a new faucet in my bathtub/ shower, but I reused the old shower hose and head.  The new faucet flows better, but I think that there's some clogging in the old shower line?  I do not understand how, but the electical reading for the propane is indicating a full tank.  I have to do some electrical testing to the liquid propane/ explosive gas sensor just to see if it's getting any power to begin with?  I'm unable to find battery powered replacements, so this is going to have to be wired to the converter.  If I can figure out what's going on with it, the next task will be to determine what's going on with the hot water tank?

The sensor has an automatic shut off feature when it senses gas in the chassis.