I have a similar problem with my unit ... I am currently working on figuring out what is going on . On mine , the detector would go off every night ( we were on a 6 week trip out west ), most annoying . We could find no reason for it to go off . On closer inspection I noticed that when it was beeping , the indicator light s on it were saying that we had low voltage ... I have a digital voltage meter that said my voltage was fine . Sooo we shut the fridge off every night till we got home ( just to be safe , since it was the only thing running on propane at the time) . I took the trailer to the dealer that sold it to me and he replaced the detector . This was in September last year ... we only went on one more trip in 2015 we were plugged in on this trip so it seemed as if it was fixed . I've been getting it ready to head to Tennessee next month and the thing started going off . I checked my batteries with a hydrometer , they are good , I have at least 12.6 volts on my meter . the same low voltage warning as the first detector ... I was puzzled . I figured , if the detector says I have low voltage ... let me see what it thinks the voltage is . I disconnected my volt meter from where I normally keep it and hooked it directly to the co detector . I seemed fine . 12.6 volts . I had lights on , the TV , opened and closed the awning everything worked and the detector was happy . Then I turned on the fridge . (on propane since I was in the driveway ) It started beeping , indicating low voltage , I looked at the volt meter and it said 11 then 10.5 , down to 10 volts and continued to fluctuate in that range ... that is low voltage . I turned the fridge off and the voltage popped back to 12.6 volts . and the co detector eventually shut up .
Currently I have another volt meter on order - I want to make sure where the voltage is getting messed up before I go to the dealer ... I don't think the co detector is at fault . If you are not yet asleep ... What I am suggesting is . to get a voltmeter and ( since you have already cut the wires ) hook it up to the co detector and see what it is thinking . Another thought that I have not yet checked out is , exactly what voltage does the detector consider low.
Over the next few weeks , I will continue playing with it and hopefully will get it resolved . AND why is the fridge freaking out the voltage . Also , just to be safe , I did buy a battery powered co/lp gas detector and that has not yet indicated any type of issue .