Carrier Air Conditioner: Hissing from the outdoor unit after it shuts off

Hissing from the outdoor unit after it shuts off on a Carrier air conditioner: On the Infinity 19VS (24VNA9) a hiss is heard at the outdoor unit for a short time after the compressor stops. This is normally the pressure equalizer valve balancing pressures across the rotary compressor so the next start is easier.

Homeowner with a air conditioner problem? Call (647) 657-2977 or book a service call — licensed technicians across Vaughan and the GTA.

Applies to: Carrier Infinity 19VS variable speed air conditioner 24VNA9

Common causes of hissing from the outdoor unit after it shuts off

• Normal pressure equalizer valve operation during the off cycle

How to fix hissing from the outdoor unit after it shuts off: step by step

1. Confirm the hiss happens right after the compressor stops and fades away on its own.
2. Explain to the homeowner that this is a normal sound for this unit, to avoid a callback.
3. If the hiss is constant while running, or the system has low capacity or icing, check for a refrigerant leak and check pressures instead - that is not the equalizer valve.

If the unit shows an error code, look it up: Carrier Air Conditioner codes

Models

Carrier 2-stage 24ANB/25HNB

24ANB12424ANB13624ANB14824ANB16024ANB72424ANB73624ANB74824ANB760

Carrier Infinity 19VS 24VNA9

24VNA924VNA91324VNA92424VNA92524VNA93624VNA93724VNA94824VNA94924VNA960