Kitchen Large Electric Appliances - Freezer not Cooling

I have a subzero refri/freezer, it has dual cooling, one compressor for the fridge, one for the freezer. Back in August the freezer portion quit working, I called a subzero authorized repair man to fix.

To make a short story long he has been out 11 times, he has changed the evaporater, defrost pan refr coil, refrig. line to the defrost pan, the capillary tube from the compressor line to the evaporater, and changed the dryer twice. Charged it and pumped out the freon a couple times each visit. Well it still doesn't work.

When you first turn it on it will cool for about an hour, it works until the temp in the freezer hits 50 degrees F then stops. You shut it off for a couple of hours and it will work again until it hits 50. Now he thinks there is moisture in the line, that is freezing, he has changed the dryer twice and has blown it out with freon several times plus he has pumped the freon out serveral times.

Basically this is what it has been doing since August even after all these repairs/replacement parts.

Any ideas on what could be wrong? Any help would be greatly appreciated.

Thanks
Frank

You mean as the temp inside say drops from 70 degree room temp down to 50, it then shuts off? What stiops? Is this a result of the compreesor getting too hot?, if that is what shuts off? Or does it still run, but the temp bottoms out at 50?

Is this commercial? 11 tech visits? Over what period of time? When he leaves, does it appear it was fixed at least temporarily, but then resurfaces again? If so, how long does the unit stay good for before it fails? Has he ever came back and found the pressures have changed and he has to add more charge? He does not suspect a leak he cannot find?

You must have tons of money invested in this unit by now. No mention about the temp control, but that depends on if you tell me if the compressor is running when it hits 50, or if the compressor shuts off. Nor mention of a possible fault in the defrost cycle, either. Surely a tech, depending on what is running, could not overlook these.

You mean as the temp inside say drops from 70 degree room temp down to 50, it then shuts off?
The compressor continues to run but it quits cooling.

What stiops?
The cooling

Or does it still run, but the temp bottoms out at 50?
Yes

Is this commercial?
No it's not commercial, Subzero Model 561

11 tech visits?
Yes

Over what period of time?
First visit 8/31/09, hes coming back tomorrow morning

When he leaves, does it appear it was fixed at least temporarily, but then resurfaces again?
He says it is working but the temp inside never goes below 50.


If so, how long does the unit stay good for before it fails? Has he ever came back and found the pressures have changed and he has to add more charge?
No

He does not suspect a leak he cannot find?
No

You must have tons of money invested in this unit by now.
I only paid him $200 for the very first visit, he hasn't asked or billed for anything since.

No mention about the temp control, but that depends on if you tell me if the compressor is running when it hits 50, or if the compressor shuts off.
Compressor continues to run

Nor mention of a possible fault in the defrost cycle, either. Surely a tech, depending on what is running, could not overlook these.
He has never mentioned a problem with these.