Long story short, I've got some projects coming up where I need to maintain a consistent temp around 45 F for a few days.  Only way I know how to do that is in a fridge, or possibly by turning my extra 1/2 bath (small) into a cooler using a window a/c unit.

 

I think most window a/cs now a days have thermostat control and some of them are digital.  I'm thinking I'll need one with some kind of non-digital dial type control.  Rewire the thermostat to remain a closed circuit so that the a/c cools whenever it gets power.  Then put a separate thermostat in-line with the power cord and control the temp that way.

 

Questions are...  Anyone see a problem with this setup?  I wonder if it would harm an a/c to have ~45 F / 7 C intake air?

Problem?  Like the compressor crashing?  Residential AC are designed to handle 72--80 degree interior spaces, and when you drive the temp down below that, you increase the chance of damaging the compressor (tech talk:  low temp causes problems with the refrigerant expansion, coil icing, liquid slugging of the compressor).  Failure is not guranteed,  but success would not be expected.  IOW, you might get lucky, but probably not.  If you want refrigerator temps, get a refrigerator.  How big are the things you're cooling?  Would they fit in a food cooler where you could pack ice into the cooler?  Experiment with how much ice and how often you have to add ice, and you might get the right combo.

Thanks for the advice Pete.  I know a guy that brewed his own beer and was able to keep a small bathroom of his around 50 deg F for a while using the same method.  I guess it just depends if the a/c you have with tolerate that low a temp.  I could maybe get away with 50 deg instead of 45.

 

I came up with the idea because the only circuit I can put a new/used fridge on might overload it so this was my alternative.

"Low temp" AC is designed for just that, and further designed for a particular range.  Just as a normal off-shelf unit has trouble below 70 (space temp), a low-temp designed for 50 would freeze up at 30.  Etc.  

     And if you get the room to 45--50 for extended time, I'm not sure what happens to the structure:  you might cause moisture problems with wood.  Low temp rooms are much more heavily insulated and moisture sealed.  That's difficult to do with a typical bathroom wall.  Wood framing is designed to allow moisture to move through it.  If you vent a small room in the winter, you can get the temp range you want for some time by adjusting the fan speed per the outside temps.  Summer beer is a greater problem. 

     If you get serious about it (can you get serious about beer?), look around for small low-temp storage units.  Lots of restaurants have room sized storage units designed for various temps on the inside.  Many such rooms are bought as a package (pre wired and AC'd) and slid into the building.  They get replaced all the time, and you might catch one on the rebound.

     Of course my expertise about alchohol stops at watching ruruns of MASH.

Maybe check here, they may have a used one that they are willing to sell.

https://www.moonminisrefrigeration.com/refrigerated-containers-in-lexington-kentucky/

Check your local used restaurant equipment dealer. They might have a surplus commercial refrigerator from an establishment which went belly up during the pandemic.