lagering fridge problem

Wife bought a new fridge/freezer. I was gifted the old one to put in the garage . She retained use of the freezer for her carnivorous tendencies. I was to be granted the capacious fridge top for lagering. Bought a temp controller. As instructed, sought the help of a professional to safely wire it in. He tells me that there is only one compressor and it is not possible to independently control the fridge alone. I note that both fridge and freezer have their own on/off switches and therefore must be on separate circuits but able to call on the compressor individually when required by suitable secondary circuits. I am advised by the prof. that purchase of a separate fridge will be required. In my pre-retirement profession , it was often a wise precaution to seek a second opinion before proceeding. The presence of numerous pipes at the rear of the machine confirms that it is of the correct type. Can anyone with the relevant experience of such a combination please assist me in giving a definitive answer.

Sorry i can't help you, I use a chest freezer, so don't run into this problem. But wanted to suggest that you might repost your question in the Yeast/Fermentation subforum, might get more responses. Plus this will bump your question up in this subforum as well Good luck!

Pappers,
thanks for your advice which I will institute stat.
The singing boys have lots of interesting recipes which I will keep in mind for the future.

I cannot claim expertise, merely familiarity with the construction of the 6 fridges in my house, as well as the one that I killed by mistreatment (incorrect PID temperature controller programming). All the combination refrigerator/freezers I own have but one compressor, and more importantly, one evaporator. The evaporator is the "heat absorber". The fridge settings allow direction of more of that cooling to the freezer compartment or the refrigerator compartment, putting a greater portion of the work towards one compartment or the other. However, the two compartments can't really be independently controlled. That said, you might find that if you really bias the controls in favor of removing heat predominantly from the freezer, then you can get acceptable lagering temps in the refrigerator compartment. It's not as neat as a separate fridge with precise temperature control, but it may be acceptable "salvage" of the fridge for brewing purposes.

threedogsNE,
Thanks for your explanation which confirms the main difficulty. If I am to get on with my plan for all grain brewing with the least problems, a separate fridge is clearly the way forward and that is what I have decided to do.Thanks to others for their help also.