Banging, clanking or rattling: something is loose
Trane's guide says rattling is not normal and points to the blower wheel, a fan, fan motor, compressor, or a loose screw or bolt. A loose part inside a spinning fan destroys the fan, the housing and sometimes the coil in minutes.
What is probably happening
- A loose blower wheel or a fan blade hitting the housing. That is the loud rhythmic clank.
- A loose panel, screw or duct section vibrating. That is the buzzy rattle, and it is the harmless one.
- Debris such as a stick or a leaf in the outdoor fan.
- A failing compressor mount can bang on startup and shutdown.
Do this in the next five minutes
- Thermostat OFF for anything that sounds like metal on metal.
- Push on the furnace and air handler panels. If the rattle stops, tighten the panel screws.
- With the power off, look through the outdoor unit's top grille for sticks or leaves.
- Note whether the noise is indoors or out, and whether it happens on start, on shutdown, or all the time.
- If it is more than a loose panel, book a visit today.
Do not
- Do not run it hoping it settles. A blower wheel that is walking off its shaft takes the motor with it.
- Do not reach into the fan, even with the power off, unless the breaker is off too.
Who to call
A licensed HVAC technician
Blower wheels, fan motors and compressor mounts are inside the equipment. A handyman can tighten a panel; anything beyond that is HVAC work.
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What it should cost
$200 to $700
Blower or fan motor replacement, national range
Source: Angi, HVAC repair cost, updated August 2026. View source
National published range, not a quote for your job. The full cost table for this trade is on the hvac page.
Ask this contractor, on the phone, before anyone comes out
Tap each one as you ask it.
- What exactly was loose or hitting, and can you show me?
- Is the blower wheel or fan blade damaged, or just loose?
- Did the noise damage the coil or housing?
- Is the motor drawing normal amps after the repair?
End the call if
- A system replacement quoted for a noise with no part identified.
- A compressor diagnosis with no readings, for a noise that started after a storm or yard work.