chest freezer heat issues

So i have a question. I got a used chest freezer a month ago and am using a johnson controller to turn the thing into a fermentation chamber. I ran it at 40° for a few days to make sure it got cold (it did) before running it at 68° for the past three weeks while my latest beer ferments.

I dropped my set point to 38° the other day and the thing hasn't been able to get below 64° since. Is the freezer struggling against the high heat we've been having in Mississippi or should i be concerned that something else is wrong? I'll open the top and see where some of the condensation has frozen on the sidewall and the inside walls are cold and the outside is hot and i can hear it running. I just don't know what to make of it since it can't seem to get past 64°.

any thoughts would be appreciated.

I would be concerned. The fact that you ran it at 40 degrees with no issue, would defiantly tell me that at least the freezer should be able to get back down to that temp with no problem. And since it's not gotten below 64 means that either the freezer isn't working, the temp controller isn't working or calibrated right, or how you wired it into the freezer ( if you did it that way) isn't working.

I live in WI, and the last 2 weeks it's been in the 90's to the 70's and my freezer which is out in the garage has been running non stop but has only moved 1 - 5 degrees. so that should tell you something.

granted, it was 105° in my garage earlier, but yeah, i am concerned. I don't know what to do since it must be cooling to a point. I don't know how chest freezers work, but is it possible that only part of it is cooling and another part shutdown or is it one big loop?

I didn't wire the controller, but i can tell by touch that the freezer isn't cooling down below 40° right now.

I don't know if plugging it directly into the wall would help, or not. I can't imagine it would since the controller merely leaves the unit on and the unit isn't cooling enough, but again, there is ice forming in a few places...

yeah if you didn't mess with the wiring than the controller simply tells the unit that it's not cold enough and the freezer than keeps running till it's cold enough. Even at 105 your should only notice a 1 - 10 degree difference, unless your opening the unit all the time the temp inside should remain constant. Now it could be that the freezer can't get down to 38 degrees but like I said is should at least get down to at least 40 which is what you tested.

I would try this, remove the controller and see what temp the freezer gets down to, with electronics elimination is key to finding out what is wrong, trust me I'm in I.T, otherwise off the top of my head either the compressor is going bad, or depending on how old the unit is it needs a freon recharge.

After mine worked for 2 years, it now decided not to go below 67F sad day. What ended up happening with yours Donner? Where you able to fix it at all?