Vendo 44 Thermostat / compressor question

[OldFans]

Hello All,

I've acquired a Vendo 44 and it was minus the bottle rack and the thermostat wire was cut. I've gone over the unit the best these novice hands can and upon re-installation, here is the data set:  Note there is no bottle rack, just an empty cooler:

Thermostat set to 1:(Warmest)

Elapsed time  Radiator     Compressor     Cooler
Start                81F               81F             81F
:15                  82F               96F             65F
:30                  83F               117F           46F
:45                  88F               125F           41F
:60                  88F               130F           40F

During this hour long run the compressor never shut down. The 44 is pulling just over 4 amps total. When I turned the thermostat to off, the compressor did shut down but I noticed a flash of green/blue light on the back wall of the cool where the cold air rises behind the evaporator fan.  Doubt this is normal unless you all say it is.  I get good frost on the outer most ring of the evaporator coil and it dissipated quickly once I unplugged.  It is running at 17F.  The thermostat pic shows it not touching anything in the cooler box or the evap coil.

Replace thermostat? 
Did I give it enough time to run/initial cool? 
I do not want to burn up the compressor as it seems to be in good order.





Thanks in advance,
Mike

[johnieG]

You mentioned a blue-green electrical flash when you turn the thermostat to “off”, I noticed your thermostat in the picture is missing it’s end-cover, it should have a a small pressed cardboard cover over the open end, it slides into place & protects the units internal contacts from shorting out & moisture, this would explain why you saw the flash of light when the thermostat shut off.  ( yes this is normal, as the contacts switch the compressor’s electrical load directly ( no intermediate relay used) so the contacts will “arc” a little, ( Fun fact...the blue color is the electricital arc itself, the green is from the copper in the contacts  )

Also, it seems to be taking too long to cool down the empty box, unless you had the door open. The system is probably a little light on gas, or the condensor coil is plugged, bad airflow can due this too.  At the maximum setting, it should be cooling easily into the mid 30-degree range ( Fahrenheit) .  

To check the actual freon charge you will have to put a set of gauges on it, I assume this is a orignal/sealed system with no access valve(s)

[OldFans]

johnieG, Thanks much for the info.  I did open the unit every 15 minutes to take temp readings.  I am trying again this morning for 60 minutes without opening the door. I can makeshift a cover for the T-stat if we can determine if it is good.  From the photo, can you tell if this thermostat is contact or air?  I'm not sure how to tell.  Basically I am asking is if the current position is correct as I want to ensure I've tried everything before replacing the T-stat.  Yep, original closed system - both sets of coils are clean and clear and the condenser hits 17 degrees after about 5 minutes of running.

[johnieG]

Terminology; the  evaporator gets cold while the condensor gets hot ....  

I see the thermostats sensing element is an open coil sitting out in the open air, so...yes it’s an air sensing type , take note that it is also on the return-air side of the evaporator coil,so it won’t shut off until the returning air is cooled down to its set point.

Keep in mind that just because the outside of the evaporators coil is at 17-degrees this doesn’t mean the inner core is, (it’s hard to measure with the fan blade whirling about)
 
also take into account that the 44’s system is designed to cool the bottles at the bottom of the rack first, so you should be monitoring the discharge air temperature at aprox that point, not at the upper cabinet area ( notice the evap’ fan is mounted at a forward pitch so it directs the air across the bottom of the stack and then up towards the front inside of the door liner , then across the bottom of the rest of the bottles in the rack before returning, drawn down along the back wall area of the cabinet to the evaporators coils inlet side, in this case if you are trying to see the thermostat’s cut-out (off) point, this is where you should be. A bit long winded in explaining, but something to keep in mind when assessing  a cooling systems performance.

Any how, the V44 is a very small machine it shouldn’t take very long at all to cool down an empty cabinet without even a rack to chill,  it’s probably light on Freon & it can’t move the heat out of the cabinet.  Mechanically it seems to be in order,  it’s time to check the system pressure.    

It’s a heat pump, if  the system can’t move the heat from the inside of the machine to the outside area effectively due to a lack of working fluid (Freon) well there you are.

[OldFans]

Yep, everything you say rings true.  Ran it an hour, 41F at base of cooler.  Note:  The fan spins so it pulls air down from the cooler over the evap coil and pushes air up the back of the cooler tank via the small gap in the evap fan housing.  From your description it sounds like my fan is running in reverse.