Frost control

I've owned a number of pressure washers but have never seen nor heard of such an accessory. But I can't understand why you'd need such a function. It's easy to ascertain if your feed hose is frozen. And if that feed hose is clear then you can ascertain if water if flowing through machine and output hose without turning the PW on.

If you are not an experienced handyman, forget it.

If you are, then buy a digital thermostat control switch ( less than 10 bucks on ebay) and control a tree phase relay that will power your pressure washer.