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Hi, my Vendo 81A w factory deck,  was recharged w 12 oz R12 after several hours of vacuum. Machine cools down quickly to sub freezing temps. After 4 or 5 hours running, temp begins to creep up to room temp.
If I turn machine off for 30 minutes or so it will again repeat this cycle. I was thinking maybe moisture in system freezing up, although I thought this would be eliminated w 2 hours of vacuum.
Anything else I should consider?
Thanks for help!

1: If you had to put 12 ounces of Freon back into the system ( pretty much a full charge for an '81) I hope you fixed the leak. Freon just doesn't disappear from a system.

2:  Yep, it sounds like you've got Ice crystals plugging your capillary tube. if the system was leaking that badly chances are that the oil has absorbed quite a bit of moisture, I assume it's an original deck, so it probably doesn't have a filter/dryer inline with the high side where it exits the condensing coil & joins the capillarity tube, however if it does have a dryer, the desiccant inside it may be saturated with moisture & a vacuum isn't going to force it to release the absorbed water.

It would be better to install a filter/dryer & start over again. you could try to add some line dryer additive ( basically methyl-alcohol) which wont remove the water, but will lower it's freezing point to help reduce ice crystal build up, but this only works for a small quantity of moisture say one or two drops.

PS;    sub-zero in a pop machine is a bad thing, you may want to check your thermostat too.  :tounge:

Thanks for reply. Yes the leak was fixed. A new filter was installed where capillary tube goes into evaporator where the original one was. Do you have a recommendation for the filter/dryer at condenser outlet?
I just mentioned that it easily cools down past freezing, but w/ thermostat ~4 machine is at 33-34
Dave

       Are you sure you didn't remove the accumulator?

       The 81 has a filter,it's simply a screen inside the end of the tube coming out of the condenser just prior to where it merges with the cap tube.

No definitely didn't remove accumulator, there was a filter at end of capillary tube which was clogged and was replaced.
So I installed a filter on liquid line, vacuumed system and recharged with 12oz virgin R!2, now runs fine, holds a steady 34 degress at about 3.5 on thermostat.
Thanks for help.
Dave

Congratulations. It's always a little mundane detail.