Heat Pump Making Loud Noise? 6 Common Causes
May 10, 2026
Heat pump noises fall into six categories: rattling, grinding, clicking, humming, screeching, and vibrating. Each has a specific cause. Rattling and vibrating are often DIY fixes. Grinding, screeching, and continuous clicking need a tech immediately and you should stop running the system to prevent damage.
The six categories
1. Rattling. A loose panel, loose screws, or debris in the outdoor unit fan path. Walk around the outdoor cabinet and tighten any visible screws. Check for sticks or leaves in the fan blade area. Most fixes here are 5 minutes.
2. Grinding. A failing fan motor bearing or compressor bearing. Both are serious. The bearing is metal-on-metal contact; running the system accelerates damage exponentially. Turn the system off at the breaker and book a diagnostic. This is the most expensive failure on the list if ignored.
3. Clicking. A single click at startup is the relay engaging. Normal. Repeated clicking without the unit running is a failed contactor or capacitor. The fan or compressor is trying to start and failing. Needs a tech, $150-$350 typical repair.
4. Humming. Electrical issue. Could be a failing capacitor (compressor trying to start), a transformer issue, or a contactor stuck. Needs diagnosis.
5. Screeching. Compressor problem, usually internal. Worst-case of the six. Stop running the system. Compressor replacement is the most expensive heat pump repair (often $1,500-$3,000).
6. Vibrating. Loose mounting brackets, failing isolation feet on the outdoor unit pad, or out-of-balance fan blade. Check mounting bolts first. If those are tight and vibration continues, the rubber isolation feet may have degraded (5-7 year wear item).
What to check before calling
For each of the six noises, do these in order:
- Tighten visible screws on the outdoor cabinet
- Check for debris in the fan blade path (turn off first)
- Verify the mounting pad is level and the feet are intact
- Check the indoor unit front cover is fully seated and clipped
If the noise persists after these checks, book a diagnostic.
Vermont-specific causes
- Snow load on the outdoor unit pad can shift the unit and create vibration. Clear and reseat in spring.
- Cold weather contraction of mounting screws causes them to loosen each winter. Annual retighten is reasonable.
- Ice buildup against fan blades during failed defrost cycles creates intermittent screeching. Clear ice and observe the defrost cycle.
Book a diagnostic
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