Schwank prefection wall furnace thermo control

Question

We have a schwank prefection wall furnace and the temp control is very touchy. We barely move it to get a higher or lower tem and the temp in the room changes too much. This unit does not have a thermostat. It is a k**b control. Can we put in a thermostat to control the temp or do we need a conversion something to do that? I do have the book but it is unclear if a conversion kit is needed. The model ASV120David