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Refrigeration issues


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Fighting refer issues on a couple of machines:

DN 5591 - ice build up on the evap - clear block ice, not frost, looks about the size of a softball.  Cabinet won't drop below 48 degrees or so - had a tech come out put a bullet piercing valve on the low side, pressure was low, added gas, wouldn't hold pressure - 20 minute service call, not going to mess around plan to replace that deck on site - haven't done it before on a bottle drop, but have on a number of stackers.  Any tips on taking these apart?  I know the bottom two shelves have to come out and to be careful manipulating the evaporator out to avoid kinking the lines - anything else?

DN 2145 - this one is really pissing me off - pulled it off of a slow location because I got a new place that looks promising - took it to my shop to replace the bottom shelf (still had low gates and no pusher slides) - got that done and cleaned up, fired it up to make sure everything was good - was cooling great after a couple hours, cabinet around 38-40 compressor cycling like it should - next morning, entire evap covered with frost - to the point it was choking out the airflow and cabinet temp was up to 50 degrees.  Defrosted and fired back up, evap fan blowing hard, good air movement in cabinets - all seals look good, fresh plumbers putty on all through hulls - freaking thing frosted up again.  I only see the curly end thermostat, no defrost control (I think some of these had both) - I probably moved the t stat end messing around with the shelf it is back where it should be...2" from the evap, not touching metal.

This machine has been serviced before - there are two schrader valves - one on top of the compressor (suction line?) and one down by the fat bulb heading toward the condensor - is this the high side?  (sorry no pics - will try to get some tonight)  I have no intention of messing around with charging this thing, but kind of would like to know what the pressure is on the low side - have a set of yellow jacket AC manifold gauges that are pretty decent, was thinking I'd check pressure to at least see where I am at - just want to make sure I have the right fitting - have read on here that low side with compressor running should be around 18-20 - that sound right?


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On the 5591, did the tech defrost the evaporator first?  If not then he won't get any proper readings and he wasted his time.  If he did then you have a large air leak, bad valves in the compressor, it's overcharged or it's undercharged or it has a large freon leak.

On the 2145, there is no point in putting a gauge on the low side, and you're correct that a properly charged system that all fans run on will be at 18-20 lbs on the low side when properly charged up.

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