Battery temp.....

[oscarvan]

You guys know that diesel engines aren't the CO threat that gas engines are.

PO put it in.....

[Captain Ralph]

My co alarm went off when we varnished inside, didn’t like the smell I guess. John

Varnish or paint fumes, Battery gasses, Last nights baked beans, Bic lighter will set off any better CO alarm.
It may not be looking for CO, just anything less than the expected O2 level.

[Beachcomber]

You guys know that diesel engines aren't the CO threat that gas engines are.

My insurance required a hard wire unit and even specified the manufacture and model number.
And yes when I equalize the batteries with out opening the windows and doors it goes off.