Noise · Denver
Why does it knock when it shuts off?
The short answer
A knock as it shuts down comes from the machinery bay, and Sub-Zero counts banging from that area among the ordinary running noises. What matters is whether it is new or louder. Sub-Zero Appliance Repair Denver will listen — (303) 729-0972.
$89 service call, credited against the repair.
Before you call
- Count how many knocks there are. One as it stops is a different animal from a run of them while it works.
- Note the time of day it bothers you. A quiet house at night makes the same noise sound worse, as the manufacturer points out.
- Close a door or a drawer and listen. A knock that stops once a compartment is shut is coming from inside it.
- Look at the coil through the lower grille; a loaded condenser is the first thing to rule out on any new noise.
Stop here and call Sub-Zero Appliance Repair Denver on (303) 729-0972 if the knock now repeats through the cycle instead of once at the end.
What it usually turns out to be
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The machinery settling as it stops
One knock, always at the end of a run, the same for months, and nothing else about the cabinet has changed.
Quoted after the diagnosis
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A noise carried by the house
It sounds worse at night or in an open plan room, which is exactly what the manufacturer says to expect.
Quoted after the diagnosis
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A fan knocking as it slows
The sound comes from a compartment rather than the floor, and it stops while that door is standing open.
Evaporator or condenser fan motor$320–$740
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A condenser left too long
The cabinet has got noisier in general, the runs are longer, and the coil behind the grille wears a grey mat.
Quoted after the diagnosis
When it is worth a visit
One knock at the end of a cycle, unchanged for years, is not a repair. A knock that has appeared, doubled up, or moved into the middle of a run is worth a technician hearing while the cabinet is still doing it.
Where a knock comes from
The bay at the bottom of a built-in holds heavy parts under changing pressure, and it stops and starts many times a day. Sub-Zero’s guidance on that area is refreshingly blunt: banging, clicking and rattling all belong to normal operation, and they carry further in a house with hard floors and few doors.
So the diagnosis here is comparative, not absolute. A knock is only information if it is different from the knock the appliance was making last season, and the difference that counts is pattern: one at the end of a run is one thing, several during a run is another.
The house is a variable too. Kitchens get remodelled, rugs get lifted, a family goes away and the room goes quiet — and an old noise turns into a new question without the appliance changing at all.
Follow-up questions
Is one knock at the end of a cycle normal?
Sub-Zero's own list includes banging from the machinery area among the sounds a working appliance makes, and adds that an open plan room or a quiet night makes them more noticeable. One knock, always in the same place in the cycle, is the ordinary version.
Why has it started knocking only now?
Something usually changed around it rather than in it. A hard floor going down, a rug coming up, cabinet doors rehung, or the house simply being quieter at present will all bring a noise forward. The other possibility is a coil nobody has cleared in a while.
What should I say on the phone about a knock?
When it happens in the cycle, how many knocks there are, whether it changes with a door open, and when it started. Sub-Zero Appliance Repair Denver can usually name the likely part from that description before anyone lifts a grille off.
Talk to someone
Still doing it after the checks?
Say what changed and in what order, and the technician packs for that fault rather than for a guess. Technicians work 8:00 am to 8:00 pm, any day of the week, and the line takes a call 24/7.