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Jason, Home Appliance Technician
Category: Appliance
Satisfied Customers: 410
Experience:  Home appliance technician with 10 years experience working on numerous makes and models.
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we have a sub zero built in over and under must be 10 nyears

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we have a sub zero built in over and under must be 10 nyears old once in a while I hear a knocking sound and the upper drawer (fridge is not cold enough
Do you hear the knocking from the top of the unit or from inside of the drawer that is not cold?
Customer: replied 4 years ago.
the knocking sound id actually on the middle of the unit almost the bottom part where the freezer section is
If you open the freezer drawer, does the noise stop? It says vacuum condenser (filter) on the display?
Customer: replied 4 years ago.
yes the sound stops. the tech is here yesrterday to service the washing machine maytag neptune to replace the motor because the circuit board crap out. anyhow we ask him to see and might just be the filter.

That vacuum light indicates that the compressor is running for a long period of time. Usually the fault is that the condenser is clogged with dust. You can try vacuuming it, but it doesn't necessarily mean the condenser is clogged, that light is like a check engine light on a car, it just means something is wrong with the cooling system.


If you have a knocking noise and it stops when you open the freezer door, this leads me to believe the issue is the evaporator fan. This fan turns off when you open the door and is responsible for circulating cold air throughout the freezer. If it is noisy, it is either defective or hitting something that is causing it not to spin efficiently.


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