Beeping Sound Eminating from 12V?

Not aware of this beep, maybe @ChapmanF has?

Suspect your 12volt is getting old... In general Prius don't charge the 12v very well and you're gonna need to put the 12volt on a legit battery charger that goes up to at least 8 amps periodically to keep the battery healthy, especially if you're using your 12volt to live in. It might be wise to have a second 12v stashed away in the car too...

 

I put a battery with like 9 to 11 volts in it Just messing around with the car The car was running and everything was running fine and even when I short the battery with my battery tester the old style with the heavy cables in it that literally turn red if you leave the switch down long enough. No beeping heard then I killed the battery because it's no good anyway this was just a test but no beeping did I get so I'm hoping it's your fridge or your inverter or something. But I couldn't make a beep happen in the car by killing the 12 volt while it was mounted installed and the car was running and then when the car was off well it was off I didn't try it in the accessories mode maybe I should have.

 

I googled a bit and there were a lot of reports about Dometic 12V fridges beeping, mostly as door open warnings. Perhaps the door switch on the fridge is going and the vibration from its motor kicking in is enough for a brief door warning beep? Can you make the sound stop by holding the door shut, or by damping the motion of the fridge by putting a hand on its various surfaces?

There was one thread though about inverters beeping because of excessive current draw from a fridge:



Maybe the Prius beeps when excessive current is drawn from one of its 12V outlets, even briefly?

I suspect that the sound is coming from the fridge itself, especially since it syncs with its motor. Try pulling the refrigerator out of the car, some place quiet, and hook it directly to an isolated 12V battery (not necessarily the one in the Prius) and have a listen. Batteries don't beep, so if you hear the beep in that situation it is the fridge, even if it isn't easy to tell where in the fridge it is coming from.

 

Also, I just noticed that the fridge is now 2 years old. That's enough time for something to break or wear out in a small device like that. I would suggest searching for that model and see if anybody had reported a similar problem. Probably wouldn't hurt to clean the cooling coils, assuming it has some.