Fountain Valley: noise from the AC and what it means

A surprising number of Fountain Valley calls we run start with “my AC is making a weird noise.” The good news is the type of noise usually tells us what’s wrong before we open a panel. The bad news is some of those noises mean stop using the system now.

What different noises mean

A short rundown of what we hear and what it usually is:

• Buzzing or humming with no fan spin: failed capacitor or stuck contactor
• Grinding or screeching from the outdoor unit: failing fan motor bearings
• Rattling that gets louder as the unit speeds up: loose panel or fan blade
• Hissing or bubbling: refrigerant leak somewhere in the system
• Loud bang at startup: compressor slug, often a sign of bigger problems

The hissing and the bang are the two to take seriously. Hissing means refrigerant is escaping, which is bad for the system and worse for the environment. A slug bang means liquid refrigerant got into the compressor — repeat slugs kill compressors.

When to stop and call

If the unit is making a noise it never made before, turn it off and call before you run it overnight. We’ve had Fountain Valley customers run a noisy unit for two weeks “until they had time” and turn what would have been a 300 dollar repair into a 3,000 dollar one. The compressor is the expensive part. Anything that protects it is worth doing. See more on AC repair.