Routine Systems Check

Quick Systems Check for Sub-Zero Fridges

Difficulty: Medium to Hard

We will go over how to test out very basic functions on your Sub-Zero fridge. This will not give us a concrete idea of what is wrong with the machine but rather isolate issues and give us framework to work within to figure out the issue at hand.

Is Your Evaporator Fan spinning?

Does the interior fan spin when you depress the switch located on the door? The interior “Evaporator fan switch” is almost always being depressed by the door or a mechanism attached to the door, to test, simply locate it and press it with your finger.

Is Your Condenser Fan Spinning?

Remove baffle to expose the mechanical shelf. On the right side you will see a fan. It will be facing the condenser, and is intended to suck air through and over the mechanical components. If the fan is not spinning you should determine if it is receiving electricity. To do this use your Non-Contact Voltage Tester, and touch it to the wire which connects to the fan. If there is no power going to the fan, there is probably a thermostatic issue. If there is power going to the fan and it isn’t running, then the fan has most likely died, and needs to be replaced. If the condenser fan is broken and not running the mechanical shelf will become very warm, and the compressor will be hot to the touch.

We must first know if the compressor is receiving electricity, and if it is running. In almost all cases, if the interior evaporator fan is running when the switch located on the frame is depressed, power is running through your circuitry and will most likely be reaching your compressor. This “fan switch” is almost always being depressed by the door, to test, simply locate it and press it with your finger. If your fan spins on the interior of the machine, we can proceed to the next step.

Locate your compressor, test it for electricity.

Your compressor is located on the mechanical shelf behind the baffle. Remove the baffle to expose the compressors. Most units have a refrigerator and freezer compressor, the smaller of which is the refrigerator compressor. In order to check if the compressor is receiving power you must locate the wires entering the front of the compressor, these will usually be grey, purple and/or white. Use your Non-Contact Voltage Tester to identify if electricity is running through these wires by touching the tip of the pen to the wires. If the pen shows a red light and beeps you have power coming to the compressor. The next step is to determine if the compressor is actually running. A technician would use a refrigerant gauge, but for the purposes of this article we will simply have you touch the surface of top of the compressor to feel for vibrations. A vibrating compressor means it is running, however it does not indicate its efficiency. A running compressor is not necessarily an efficient one, however more times than not they are OK. If  your compressor is not receiving electricity and your machine is not achieving the desired temperatures, then most often your Thermostat would be at fault. If your compressor is running, its fans are spinning, and the units condenser is clean, then a fault would more than likely be within the “sealed system” and a refrigerant pressure reading from a professional would be advised.

Is your door gasket in good shape?

Another way to check the efficiency of your system is to review the integrity of your door gasket. The gasket is the white rubber strip that contacts the frame of the unit and ensures the door stays closed. Over time gaskets may tear or warp, causing the integrity of the seal to fail. If the door does not close fully it will not activate the switches which cause the machine to run efficiently. Often times gaskets are misdiagnosed as the problem because they loose the ability to seal tightly. This is often due the fact the machine is no cold enough to create a good seal and has little to do with the gasket. If your gasket is ripped you are more likely to experience moisture inside the box. Rarely do we find that temperature issues are directly related to gaskets, but it is possible.


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