In the past 6 years I have had two 14 cu ft chest freezers, which I had converted to keezers, fail on me. Admittedly I bought them at garage sales for <$50 each, but they were running and freezing well. In each case I used my old Johnson Controls analog controller to keep the temperature 47-52 degrees, and in each case everything worked well for a year or so, then the freezer failed (stopped working). So the question is: did they die of old age, or is there something inherently destructive about running a freezer at refrigerator temperatures. Is my experience unique? Am I doing something wrong? I should note that I had them on a screened-in porch in southern Arizona, where the summer daytime temp can reach 95F (but its a dry heat!)
I’m really reluctant to buy a new freezer to convert to a keezer if using it this way will cause premature failure.
Is this a keezer with a collar and taps? Or do you open the lid and use picnic taps?
Where is arizona do summertime temps reach ONLY 95? did you mean 195? 
I had one 6-head mushroom tap and two two-head taps, for a total of 10 taps mounted on the lid thru three holes which were well-insulated with spray insulation. There were no cooling lines in the lid.
We rarely get over 100. I live in the mountains of southern AZ (Sierra Vista), only 5 miles from the border.
I can only speak to my experience but I purchased a new 7.5 CF freezer 5 years ago (I think, maybe 6) and use a Ranco digital controller. It is still working great.
My experience with used, direct purchase, appliances is that they were replaced for some reason. I don’t typically expect much out of them. Many people would say I have a massive pessimistic outlook on the world (think Eeyore or Marvin) but I am not surprised by failures.
If I were you, I would buy a new one. Treat it right and you may be pleasantly surprised.
Paul
The only thing that comes to mind is “short cycling” the compressor motor. This happens when the on-off points are close together and when the probe reacts quick to temperature changes in the freezer. What happens is that the motor turns on, the freezer chills and shortly after the measured temp is low enough to shut the motor off again.
compressor motors don’t like to be turned on and off a lot.
Some temp controllers have protection for this preventing the motor from turning on during a set period of time after it was turned off last.
If your temp controller doesn’t do that, I suggest placing the probe in an empty bottle and close the bottle with a paper towel plug. This will slow the time with which the probe reacts to temp changes.
Kai
I echo Kai’s line of thinking.
And, these chest freezers aren’t meant to be kept outside in warm temps- a balmy 95* might be too much for them and they are cycling too often.
Maybe not cycling too often in that heat, but just running a lot a lot.
I have a related question. I bought some plumbers putty for something (brewing related, of course, I have no handiness outside that), and I ended up using a hunk of it to completely cover the probe, probably about 1" around outside the probe.
Do you think this is helping reduce the frequency of on/off cycles?
yes
Kai
Darn it. You jinxed me 
I too have a broken freezer chest now. This one ran for 6 years in my basement and now it doesn’t cool anymore and I hear liquid gurgling inside.
I doubt there is much that I can fix 
Kai
You must be pretty high then, and I bet the altitude is making it harder for the compressor to operate. It rely’s on outside air to cool the coils and if the air is less dense then it does a poor job of cooling. The short cycling is always what kills freezers. Altitude and heat add to stress on the compressor.
Sad story Kai 
I have 3 vintage chest freezers currently. A couple of years ago I had another fail (for some reason, but Kai’s liquid gurgling dredges up some memories). If you are going to keep your analog controller, then keep the bulb immersed in a volume of inert liquid (say a quart milk jug). That will keep it from responding too quickly to temp changes, especially if you have it taped close to the freezer wall. Do you have a fan running inside the freezer? That will go a long way to keeping the temperature even throughout the inside space. When the compressor kicks off, you want to make sure it stays off for at least 5 minutes, as the man says, short cycling kills freezers. The Johnson A419 digital controller has a settable short cycle delay (as do the Love controllers), but the probes are not waterproof. The Ranco controllers do not have the delay timer, so for those, a thermowell is required. My freezers are in my garage which stays upper 90s to 100 easily here in North Carolina. When they run, they run for 20-30 minutes, then shut down for at least a couple of hours. In the winter, they can go for days without coming on at all.
Thanks to all who responded for all the input and food for thought. The message that came thru loud and clear that I have to reduce the cycling to prolong compressor life. I can’t do anything about the altitude (5300 ft), and I can’t keep the keezer in the house. So I will buy a new chest freezer and a new digital controller, and keep the sensor head in a gallon jug of water to act as a thermal buffer and reduce the frequency of cycling. Now I just have to keep my eye on the sales to get the best bang fory buck.
Again, thanks for the help.
Don’t mean to hijack but I wanted to reply to Kai on something. I have a love controller and the probe doesn’t seem like it’s supposed to be submerged in water. If I take an old 20 ounce soda bottle, drill a hole in the cap and put the probe in there with just air inside, I think this would reduce the amount of cycling the motor does. Every time I open the freezer the air is moved around and I notice the temp swings a degree or two but I suspect it would normalize once I close it again. Any reason this wouldn’t work?
I actually think that is what Kai was suggesting.
That’s what I thought too. Thanks!
I actually use a White Labs vial to keep the probe in. Just like brewmichigan I drilled a hole into the cap.
I think some brewers may be taking recommendation about minimizing temp fluctuations as a recommendation to minimize temp fluctuations in the ambient fermentation temperature. It’s perfectly fine for the ambient temp to swing by +/- 5 F or more. The thermal mass of your fermenter will even that out.
Kai
I have the temperature probe for my keezer in a block of solid foam insulation. Same effect as a bottle of liquid without the worries about liquid.
This bears the question, how much lag between ambient temp and probe would be too much? I.e. when are the temp swings so drastic and low frequency that there are noticeable temp swings in the fermenting beer.
Kai