With the thermostat in and the cooling system CLOSED like it should be, you may see the temp creep up to 190.....maybe even breach 200, but then when the thermostat opens, it will cool back down. And of course if for some reason it does not, just cut it off. That probably means it has air trapped behind the thermostat and make take a time or three of running it and letting it cool back down before it gets out.