1954 Philo Tru-Zone Question | MonitorTop Refrigerator Forum

rexc
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Posts: 31

1954 Philo Tru-Zone Question Jun 21, 2022 18:28:14 GMT jake and ckfan like this

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Post by rexc on Jun 21, 2022 18:28:14 GMT

Gang,

You all have tried to help me with my Tru-Zone cold plate freezing up on my 1954 Philco refrigerator freezing up. This has been going on for years now. The unit cools fine, but the Tru Zone no longer defrosts itself as it used to. Several people have suggested that the cold control may be bad or loose, but I recently learned that there are what appear to be two thermostats in the unit. The main control is a dial type that goes from Off to Hard Freeze, and that is the one I have always used and keep at the lowest setting. However today, I discovered that there is another control hidden behind a plug inside the cabinet below the Tru Zone plate. It adjusts with a screwdriver and has only an arrow that says COLDER with a right turn. There also appear to be some numbers there. It was on its coldest setting, so I have reduced it. Could it be that this controls the Tru Zone on and off and the main control controls the Freezer? The freezer, which has an internal door and is the upper part of the unit, frosts up about like you would expect for a non-self defroster.

I have been looking for a repair manual or even owner's manual for a long time, and have never found one. Have I shared enough that someone can help with this? I am defrosting now in hopes that I have discovered something.

Thanks!

REx

ckfan
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1954 Philo Tru-Zone Question Jun 23, 2022 15:30:25 GMT via mobile jake likes this

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Post by ckfan on Jun 23, 2022 15:30:25 GMT

That is really interesting. I honestly don’t know how those Philco fridges work. I suspect you are onto something though. My guess is that the thermostat in plain view is sensing the temp of the freezer. I know that on GEs of this era, they had a refrigerant control valve that allowed a controlled amount of refrigerant to enter the fridge section evaporator. I’m guessing that is similar to what you are describing.

I have to keep telling myself that this is a healthy addiction!

It is all in the name of preserving and enjoying these wonderful machines.

rexc
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Posts: 31

1954 Philo Tru-Zone Question Jun 25, 2022 13:39:22 GMT jake and ckfan like this

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Post by rexc on Jun 25, 2022 13:39:22 GMT

Thanks for the reply. I seem to have made some improvement by attempting the synchronize the two controls; however, I still can barely turn the visible control on without upsetting the defrost feature in the refrigerator. Maybe one day I'll find a repair manual that will explain the settings. What you are saying about the GE units makes sense! Thanks, Rex

jake
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1954 Philo Tru-Zone Question Jun 26, 2022 12:37:48 GMT via mobile ckfan and turbokinetic like this

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Post by jake on Jun 26, 2022 12:37:48 GMT

From what I've read about these the hidden thermostat is for the cold plate in the refrigerator compartment only. It works opposite from a conventional thermostat in that it turns on when the cold plate gets down to a predetermined temperature to energize a solenoid that shuts off the refrigerant flow to the cold plate. The thermostat that you can see and adjust controls the compressor cycling and senses the temperature in the freezer compartment. It works as a conventional thermostat, turning the compressor off when the freezer compartment gets down to temperature. So, a normal run cycle would be the refrigerator is off. The solenoid for the cold plate is not energized so it is open to allow refrigerant to flow through the cold plate. When the freezer compartment temperature rises and the user thermostat, that you can see and adjust, calls for cooling and the compressor turns on. Right now both the freezer compartment and refrigerator compartment are being cooled. Since we don't want the refrigerator compartment to be below freezing temperatures the cold plate thermostat, which is hidden, is satisfied first and turns on sending power to the solenoid and the solenoid closes, blocking refrigerant flow through the cold plate. The compressor continues to run until the freezer compartment is brought down to temperature. When that happens the user thermostat shuts off the compressor. In the meantime the cold plate has been warming up to above freezing temperature, even though the compressor was still running. The hidden thermostat will switch off after the compressor stops. So even though the cold plate is technically calling for cooling it will not get any until the compressor cycles on again. This is more than enough time for the cold plate to defrost in between run cycles of the compressor. If I had to guess I'd suspect either the hidden thermostat or the solenoid is bad. If you find the hidden thermostat is bad keep in mind it works opposite of a conventional thermostat and must be replaced with the correct thermostat for your refrigerator. I'm wondering if it's been replaced in the past with the wrong thermostat and/or the solenoid was really the problem to begin with. Hopefully this will help.