You are correct, there is no 'on-off' switch on those motion sensor lights. If it is failing and you want to keep it, then replacement is your only choice. If you do replace it, why not install a simple toggle on-off switch also, so if you want it truly "off" it will be "off". I cut the wires on mine completely. I hate the thing. As soon as you open the outside door at night, that BRIGHT light blinds you and you can't see a thing. Why they put it FACING the door is beyond me.
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2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually