A heat pump is not a silent appliance. It moves a lot of air and it runs a compressor outside your house, so there is always a baseline of sound. The useful question is never "is it making noise" — it's "is it making a new noise."
That's the whole diagnostic. If the unit sounds different than it did last season, something changed. Here's how we sort those sounds when we get the call, what each one usually costs, and which ones mean shut it off right now.
First: what a healthy heat pump sounds like
Modern outdoor units typically run 55 to 60 decibels on high speed and 45 to 52 decibels in low or quiet mode. That's a dishwasher, or two people talking in a kitchen. Ductless mini-split indoor heads are quieter — often 19 to 30 decibels, which is why people forget they're on.
Normal sounds you don't need to worry about:
- A low, steady hum from the outdoor cabinet while it runs.
- Air movement at the supply registers, or a soft fan whir at a mini-split head.
- A quiet click when the system starts and stops.
- Occasional gurgling or a soft trickle from refrigerant lines.
- The defrost cycle. Every 30 to 90 minutes in cold, damp Puget Sound weather, the reversing valve shifts with a whoosh or a hollow clunk, the outdoor fan may pause and restart, and steam pours off the coil. It runs 5 to 15 minutes. This is the machine working correctly, not failing.
Buzzing or humming that won't stop
A buzz is almost always electrical or mechanical vibration, and it's the most common noise call we get.
The likely causes
- A loose service panel. Sheet metal vibrating against the cabinet at a specific RPM. Genuinely a screwdriver fix, and worth checking yourself before anyone charges you a diagnostic.
- A failing contactor. The relay that closes to start the outdoor unit. When the contacts pit and burn, it buzzes and sometimes chatters. Cheap part, common failure.
- A weak capacitor. Capacitors give the fan and compressor motors the kick they need to start. A dying one causes a hum with no start, or a struggle-then-start. Also a low-cost part.
- Refrigerant line contact. A copper line resting against framing or siding transmits compressor vibration straight into the wall. Isolating it with a hanger or a foam pad ends it.
- The pad itself. Composite pads that have settled unevenly in soft Puget Sound soil turn the whole unit into a drum. Re-leveling solves it.
A hum with no airflow and no fan movement is different — that's a motor trying and failing to start. Shut it down and call. Running a stalled motor cooks the windings.
Most buzz-category repairs sit at the low end of the $150 to $1,500 typical heat pump repair range for standard markets ($175 to $1,800 in affluent markets, $200 to $2,000 in luxury markets).
Rattling
Rattles are mechanical. Something is loose, or something got in.
- Debris in the cabinet. Fir needles, alder leaves, a rogue pinecone, bark from a landscaping bed. Our region is exceptionally good at putting yard waste inside condenser cabinets.
- Loose screws or hardware. Fasteners back out over years of vibration and freeze-thaw.
- A bent fan blade clipping the grille intermittently.
- Ductwork. Sometimes the rattle isn't the heat pump at all. A loose duct joint or an oversized plenum panel flexing when the blower ramps up sounds like a mystery bang inside a wall.
- The indoor blower wheel. Debris caught in the squirrel cage, or a wheel out of balance, produces a rhythmic rattle you can hear through the whole house.
One rattle we treat as urgent: a loud, hard rattle or clatter from the compressor area, which can mean failing internal mounts. Turn it off and get eyes on it.
Screeching, squealing or whistling
High-pitched sounds point at bearings or pressure.
- A squeal that rises with fan speed is usually a dry or failing fan motor bearing. Motors don't heal. Replacing one before it seizes is cheaper than replacing one after it takes the blade and the coil with it.
- A metallic screech from the compressor on startup can mean internal bearing wear or a serious pressure problem. This one is genuinely worth stopping the system over.
- A whistle from inside the house is almost never the equipment. It's air being forced through a restriction: a clogged filter, closed registers, or an undersized return. Change the filter and open the registers first. If it persists, it's a duct sizing issue — real, fixable, and cheaper to diagnose than to guess at.
- A shriek or hiss with a chemical smell near the lines suggests a refrigerant leak under pressure. Refrigerant work is licensed work, and topping off a leaking system without finding the leak is money set on fire.
Grinding, scraping or banging: shut it off
There is a short list of sounds where the right move is to stop running the machine.
| Sound | What it usually means | Action |
|---|---|---|
| SoundGrinding | What it usually meansMotor bearing failure, metal on metal | ActionShut off, call |
| SoundScraping | What it usually meansFan blade contacting the cabinet or coil | ActionShut off, call |
| SoundHard bang at startup | What it usually meansCompressor mount or internal failure | ActionShut off, call |
| SoundRepeated loud clicking with no start | What it usually meansFailing control or capacitor | ActionShut off, call |
Switch the thermostat to off, then pull the outdoor disconnect if you're comfortable doing it. The reason isn't drama — it's that these noises mean components are already touching each other. Twenty more hours of runtime is how a $400 fan motor becomes a compressor conversation.
If the noise came with the system not producing heat, our heat pump not heating walkthrough covers the free checks in order before anyone pays for a diagnostic.
The five-minute check before you call anyone
- Change or check the filter. A clogged filter causes whistling, straining and sometimes an overheating blower. Free.
- Clear two feet around the outdoor unit. Blackberry canes, ivy, sword fern, stacked firewood, garbage cans. Airflow restriction makes everything louder.
- Look for standing debris in the top grille. Power off first. Do not reach into a fan.
- Press on the service panels. If the buzz changes when you touch the cabinet, it's a panel or a mount, not electronics.
- Check for a downspout or gutter dripping onto the unit. Common here. It causes both noise and icing.
- Time the noise. If it starts and ends on a 30-to-90-minute rhythm in winter, you've identified defrost.
If all six pass and the noise is still there, it's a real repair, and knowing which category it falls into makes the visit faster.
What noise repairs cost in the Puget Sound area
Repairs run $150 to $1,500 in standard markets, $175 to $1,800 in affluent markets, and $200 to $2,000 in luxury markets. Capacitors, contactors, hardware and debris removal live at the bottom. Fan motors and control boards sit in the middle. Compressor and refrigerant work is the top of the range.
We give you the price before work starts. Every time.
When to stop repairing
The rule we use out loud with homeowners: if the system is under about 10 years old and the fix costs less than half the price of replacement, repair it. At 12 to 15 years, especially with a failing compressor or old R-22 refrigerant, put the repair money toward a new system instead. Replacement runs $10,000 to $16,000 in standard markets and comes with our 10-year parts and labor warranty — see heat pump cost in Washington for the full breakdown by home type.
Qualifying heat pump installations can also draw up to $4,400 toward the project when replacing an existing electric or fossil-fuel system; the exact amount depends on what you're replacing and what you install. Programs change — we confirm your current eligibility and handle the paperwork. From April 2, 2026, PSE rebates require a PSE-certified installer. Varsity is one.
Noise you can prevent
Most of the noise calls we run were avoidable. Annual maintenance catches loose hardware, dirty blower wheels, drifting refrigerant charge and worn bearings while they're still cheap. Coastal homes in places like Des Moines, Gig Harbor and Steilacoom take that further — salt air corrodes outdoor hardware and coils faster, so semi-annual service and corrosion-resistant coil coatings are worth the money there.
Placement matters too. A unit on a solid, level pad, away from bedroom windows and shared property lines, with clearance around it, is quieter for its entire life than the same equipment crammed against a fence.
Get it diagnosed
If your heat pump is grinding, screeching, or buzzing in a way it never used to, don't wait for it to quit on a cold morning. Call (253) 785-4622 — Monday through Friday, 8 to 6, with same-week scheduling — or request an estimate and we'll tell you what we find and what it costs before we touch anything.
If the answer turns out to be a new system, you can see real starting numbers for your home in about 60 seconds with our instant estimate tool. No phone call required to get the ballpark.
We're heat pump specialists based in Federal Way, owner-operated, and we answer the phone after the check clears.