I think that the O.P. is telling us that it is a 12 volt CO detector. If it is attached to any existing switchable wires there is a high possibility that it will nor be on, especially at night. I think that most of us turn off things like the water pump, and certainly the lights
, at night, the very time when you need a CO detector.
Because of the potential risks involved, many of us hesitate to give electrical
advice to an electrical
Suffice to say that the CO detector should be wired to it's own fuse in the power chasses, but you may also want to have a very visible switch for turning it OFF when in storage as they can use enough power to drag down your battery to dead after an extended period of time.(Mine did)