So I am a newbie to homebrewing only have 3 batches in but I made the jump a while ago and bought a chest freezer for my new hobby but of-course it didn't have a temperature control and I found out I had to buy one in order for my new freezer to be useful to me. So I went online to northern brewer and got a Johnson A 419 control it seemed to get good reviews frm customers.So With no experience and no clue of how to use it, I referred to the manual and tried to get the hang of it i set my set point but I found tht the cooler got noticeably cooler then my set point after it cut off. I placed the probe dead center of my chest freezer its 5.0 cubic ft and was empty at the time I tested it out. I asked the owner of a local brewery nearby, who's always friendly to a new home brewer like myself, for some input. He told me I had bought the wrong kind ..tht I needed a 2 stage so i could run a heat source to on and the other to my chest freezer simultaneously . I live in Southern California rarely does it get too cold to brew the problem is it getting too hot. The A419 allows a heat mode if necessary in case I would need it though. My question is is it really necessary for me to have both a heating and cooling source simultaneously working to get a nice controlled fermentation?? I'd appreciate any help thanx in advance.