Temp control in a refrigerator

I'm interested in doing my first lager kit. Why do you have to have a special temp control device for your lagering fridge? can't you set the internal temp control with some trial and error and a thermometer to be in the range you need? Thanks

Most refrigerators cannot maintain 50F, which is needed for the fermentation.

Yeah, it really depends on what phase of the lagering process you are talking about. Like David says, people get external controllers for the initial ferment because the fridge will always get colder than 50 without it and 50 is the temp you need for lager fermentation.

For the lagering itself, no, you don't really need an external controller, just a good fridge that will maintain as close and steady to 34 degrees as possible.