Older Kegerator - Cooling?

[frostfractalbeer]

I recently got an older used Danby DKC644BLS 2 tap kegerator for free. I've plugged it in and the evaporator fan in the back runs but feeling the compressor I'm not sure if it is running or not. The last 2 days I've had my temp probe in there and while the unit is set for 40 degrees it seems to run but fluctuates an air temp between 28 and 48 degrees with an ambient temp is in the mid 60s. I find it hard to believe that just an evaporator fans and coils can cool down to that level without the compressor. I've taken it apart and verified that the power board is switching to 120v. Right now I just have sparking water and can deal with this temp variance but want to get it more stable for my homebrews. These units 644 and 645 seen to be reliable from my searches but sometimes require some modifications.
Any thoughts on maybe changing the thermistor to achieve more consistent results or might this unit be a loss?

 

[Broken Crow]

I recently got an older used Danby DKC644BLS 2 tap kegerator for free. I've plugged it in and the evaporator fan in the back runs but feeling the compressor I'm not sure if it is running or not. The last 2 days I've had my temp probe in there and while the unit is set for 40 degrees it seems to run but fluctuates an air temp between 28 and 48 degrees with an ambient temp is in the mid 60s. I find it hard to believe that just an evaporator fans and coils can cool down to that level without the compressor. I've taken it apart and verified that the power board is switching to 120v. Right now I just have sparking water and can deal with this temp variance but want to get it more stable for my homebrews. These units 644 and 645 seen to be reliable from my searches but sometimes require some modifications.
Any thoughts on maybe changing the thermistor to achieve more consistent results or might this unit be a loss?

My first thought would be to just bypass the thermistor and use an inkbird or equivalent with a better situated temp probe....but I do have brain damage and difficulty with these things I used to do. What I do recall is that though Danby's are ususally reliable until they leak or simple tarnish of components, maybe especially that copper coil 'temp sensor' and the contacts of the rheostat exposed to internal humidity give way over time.
Just spit-ballin'

 

[mac_1103]

The last 2 days I've had my temp probe in there and while the unit is set for 40 degrees it seems to run but fluctuates an air temp between 28 and 48 degrees with an ambient temp is in the mid 60s. I find it hard to believe that just an evaporator fans and coils can cool down to that level without the compressor.

I would guess that the compressor must be running if it's cooling to those temps. Try putting the probe in a glass of water or something to get more stable readings.

 

[frostfractalbeer]

I just dropped my temp probe into a vase of water. Will give it a few hours to cool to temp.

 

[day_trippr]

I just dropped my temp probe into a vase of water. Will give it a few hours to cool to temp.

So you are using an external "add-on" controller and not the built-in thermostat?

Cheers!

 

[frostfractalbeer]

No modifications to the unit but knowing these had issues I'm using my kitchen thermostat (now in water) to monitor the temp to see if my unit has issues. No connection to the unit's controls only trying to figure out if I need to replace the built-in thermistor.

 

[whoaru99]

Right now I just have sparking water and can deal with this temp variance but want to get it more stable for my homebrews.
Any thoughts on maybe changing the thermistor to achieve more consistent results or might this unit be a loss?

The thermal mass of 5 gal of wort/beer will not fluctuate at those swings of air temp. It will achieve a pretty stable average, for lack of better terms, at some point within that range.

A glass of water will dampen it to some degree but likely not as much as 5 gal (or whatever).

Put a 5 gal pail of water in there and monitor the water temp rather than the air temp.

 

[frostfractalbeer]

Updating here. My 2nd 5Gal is at 43 degrees. Still dropping but slowing down over the last 12 hours.

 

[day_trippr]

I'm using my kitchen thermostat

Thermometer?

I suspect cooling curves are not linear as there's a thermal dynamics law about increased transfer rates with increased differential...

Cheers!