heat pump troubleshooting
Heat pump is making a loud or unusual noise
What it probably is, what you can safely check yourself, and the point where it becomes our job.
Do not wait this one out. Shut the system down and phone us — running it in this state usually turns a repair into a replacement.
What is most likely going on
Shut the system off at the thermostat if you hear grinding, screeching or metal-on-metal, because those sounds mean something is contacting something else and running it makes the damage worse. Buzzing, rattling and a loud whoosh are less urgent but all point at identifiable causes.
Likely causes, most common first
- 1
Fan blade striking ice, debris or the shroud
A blade clipping accumulated ice, a fallen fir branch, or a bent shroud produces a hard rhythmic knock or scrape at fan speed. In this county it is often a limb or a chunk of frost from a stalled defrost. Running it bends the blade further and can take the motor bearings with it.
- 2
Failing fan or blower motor bearings
Dry or failing bearings screech on startup and settle into a grinding hum, and the sound usually gets worse over weeks rather than appearing overnight. Replacing a motor is a routine repair; replacing a motor that seized and cooked its wiring is not as tidy.
- 3
Electrical buzzing at the contactor or a failing capacitor
A loud hum or buzz from the outdoor unit without the fan turning usually means the contactor is chattering or the compressor is trying to start against a weak capacitor. This is not something to investigate yourself, because the panel is energised even when the unit appears off.
- 4
Loose panels, missing isolation pads or a resonant mounting surface
A rattle or drone that seems louder inside than out is often a panel screw backed out or an outdoor unit bolted to a hollow deck that acts as a sounding board. Relocating to a solid pad or adding proper isolation fixes a complaint we hear often on narrow city lots.
- 5
Reversing valve shifting, which is normal
A loud whoosh or a brief hiss as the system enters or leaves defrost is the reversing valve changing position and refrigerant redistributing. It surprises people in their first winter with a heat pump. If it happens a few times a day in cold, damp weather, it is the system working correctly.
What you can safely check yourself
Work down the list before you book anything. Plenty of calls end here, and we would rather you keep the money.
- Shut the system off at the thermostat if the sound is grinding, screeching or metallic, and leave it off.
- With the system off, look for fallen branches, leaves or ice inside the outdoor unit and clear what you can reach.
- Note whether the noise comes from the outdoor unit or the indoor air handler, and whether it happens at startup or throughout the run.
- Check that the outdoor unit is sitting solidly on its pad or bracket and is not resting against siding or a fence.
- Record a few seconds of the sound on your phone; it genuinely shortens the diagnosis.
What is deliberately not on that list
Nothing above involves refrigerant, gas piping, or opening a live electrical panel. Refrigerant work is federally regulated and needs recovery equipment. Gas work done wrong kills people. An energised panel turns a $300 repair into a hospital visit. Electrical work on the circuit itself is done by a licensed electrical contractor. If a step you have read elsewhere involves any of those three, stop and call instead.
When to call us
Call us immediately for grinding, screeching or metal-on-metal, and leave the system off until we look at it. Buzzing at the outdoor unit is also a same-day call, since a chattering contactor is an electrical fault. Emergency calls are answered 24/7 at (360) 592-3824.
Monday–Friday, 8:00 AM – 5:30 PM · Emergency calls answered 24/7
Tell us what it is doing
Describe the symptom and we will tell you what it takes to fix, what it is likely to cost, and whether it is worth fixing at all.
Monday–Friday, 8:00 AM – 5:30 PM · Emergency calls answered 24/7