500 600 series refrigerator repair

7 Steps to Diagnose Your 500/600 Series Sub-Zero Refrigerator

Posted March 12, 2020 in Sub-Zero Refrigerator Repair by Steven M

How to Diagnose Your 500/600 Series Sub-Zero Refrigerator

Well-made and reliable 500 Series Sub-Zero refrigerators are known to last for many decades until you get to experience first signs of a problem.
However, even if your Sub-Zero refrigerator stops cooling it does not mean you have to start looking for a new fridge right away – most of the time a simple fix will not only rejuvenate your appliance but also let you enjoy high-quality refrigeration for many more years!


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Step 1. Test the outlet!

test the outlet

The first thing you should do before performing any further diagnostics is to check the power outlet for proper voltage. Unfortunately, this kind of problems are pretty common, and you would be surprised how often our technicians come to the customer’s house only to discover that the source of the problem is a tripped circuit breaker. Even if the breaker is not tripped, it’s important to keep in mind that insufficient voltage would significantly reduce the performance of your appliance, even if your Sub-Zero refrigerator is perfectly functional.

Step 2. Make sure the door does not leak cool air.

make sure the door gasket doesnt leak air

Carefully examine the door seal and makes sure it is not damaged, cracked and that the door is closed snuggly. Even a small air leak could result in the hot air getting inside the refrigerator or freezer, making it nearly impossible for it to drop the temperature to the required level.

Step 3. Clean the condenser.

clean the condenser

It is recommended to carefully clean the condenser coil of your refrigerator once or twice a year in over to improve the power efficiency – a dusty condenser will make it significantly harder for your refrigerator to dissipate heat and will undoubtedly increase the cycle length, and as a result, its power consumption. In most of built-in and integrated 500 Series Sub-Zero refrigerators the condenser can be found above or below the refrigerator. You can gain access to it by lifting the front panel or removing it entirely. Depending on its position, you can choose whether you want to clean the coil manually with a brush or using compressed air or a vacuum – keep in mind, however, that you risk spreading the dust all over the kitchen.

Step 4. Make sure the fans are running.

make sure the fans are running

Sub-Zero refrigerators have at least two fans – one for each coil. Evaporator and condenser fans significantly improve the performance of your appliance – and even a single malfunctioning fan will result in significant drop of performance and could potentially prevent your appliance from reaching the target temperature. Malfunctioning motor is a common cause for a fan failure, however it would be a good idea to examine and test the wiring with the multimeter as well.

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Step 5. Test the control board and thermostat.

test the control board and thermostat

Often a faulty main board and thermostat can prevent the refrigerator from running the cooling cycle efficiently.

Even though main board diagnostic is a difficult task, both of these parts can be replaced in case you manage to successfully find the source of the problem.

Step 6. Test the compressor.

test the compressor

We recommend you to test your compressor, however, you would need a multimeter and some basic understanding of your refrigerator wiring. And don’t forget to unplug your refrigerator prior to disassembling and testing it! In most Sub-Zero 500 Series fridges the compressor is located at the top part of the refrigerator, behind a grill. Carefully unhinge and remove the grill and then the cover. Depending on the model, you may see two compressors – for the freezer and for the refrigerator. Test the compressor pins for connectivity. You may have to replace the compressor in case you find damaged wiring.

Step 7. Measure the refrigerant pressure.

measure the pressure

Unfortunately, accessing the sealed system and measuring the coolant pressure requires specialized equipment. However, if you do find out that the pressure is insufficient you can start looking for a gas leak within the sealed system. We recommend checking junctions on the tubes, especially the capillary tubes since they are most subjected to this kind of leaks. We recommend using a gas leak detector spray, however, you can also use soap or WD-40. The exact repair depends on what part needs to be replaced.

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